This bitch can't do math.

Isn't elementary geometry just knowing the main 4 shapes?

>>155905047
All I can figure out is that alpha must be less than 130.

>>155905474
your math is less than fictional elementary schooler

>>155905514
Fictional characters are naturally smarter than us

Is there a way to find out the measurements of angle EDC or DEC?

>>155905047
What if that triangle that has alpha is a similar triangle desu

I think it's just 60 or 70 ayy

It depends on what angle EDC is. All you can tell is that angle EDC cannot equal 10. As long as the angle for EDC is 11 to 139, alpha will equal anywhere from 1 to 129. Alpha cannot be 0 nor can it be 130 or higher because on the the angles in that small triangle is 50.

20 + (30 + alpha) + angle EDB = 180
angle EDB + angle EDC = 140
angle EDB = 140 - angle EDC
20 + 30 + alpha + 140 - angle EDC = 180
alpha + 190 - angle EDC = 180
alpha = angle EDC - 10, where angle EDC cannot equal 140 or higher.

It would be a world of difference if it was given that triangle EDC was an isosceles triangle instead. EDC and DEC would both be 80, and alpha would equal 180 - 30 - 80 = 70 degrees. Without knowledge of either EDC or DEC angles, then it is impossible to find an exact value for alpha using elementary geometry.

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There is no way to find this as the angles are fucked up. They don't all add up properly. shit that suppose to look like its under 90 looks like its over and vice versa. Whoever drew this is a retard.

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>>155905047
The angles of a triangle add up to 180.
The angles of a quadrilateral add up to 360.

I get 70.

Holy fuck I just derived fucking law of sines.

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>>155905047
>that one triangle with points a and b that has an obtuse angle
>the obtuse angle is 50 degrees

>>155906415
You cannot assume that it's a perfect trapezoid without any markers indicating that the segments making it up are the same length. If it were a perfect trapezoid, then it would make sense for those angles to equal 100, but for all we know one of them could 99 and the other 101. There's nothing that lets us guarantee the value of those angles.

Those angles are all fucked up, so it's not actually possible

>>155906415
On second thought, I can't assume E and D are both 100 in that second step. Scratch that.

its 65 degrees isn't it

>>155906402
i'm sorry but you are a retard

>>155906385
Glad I'm not the only one that got stuck at that point.

>>155906415
you are the only person in this thread who graduated high school math

I want to FUCK Kuro

>2 obviously acute angles
>60 and 70 degrees
Fuck that diagram

>>155905047
0?

>>155906793
Obviously it's not drawn to scale.

>>155906415
Yeah it's 70

>>155906498
To be fair this happens all the time in textbooks where the image given looks nothing like the angle listed. Unless it's telling you to measure the image with a protractor just ignore the actual angles image.

>>155906566
A square is 360 degrees anon, the pointier corners get compensated by the flatter ones

>>155906498
You're in luck! What the angles look like is irrelevant because you're not supposed to eyeball them.

>>155906415
took me a sec to see where you pulled those 100s for E and D from.

>>155905047
Just google hardest easy geometry problem for the solution.

>>155906537
Actually scratch that, I'm fucking retarded. Given that ABE and BAE are 80, then it is a perfect trapezoid, thus the answer IS 70.

>>155906914
>>155906950
The trouble is AB and DE aren't necessarily parallel, so I can't assume the two angles are both 100, only that they add up to 200.

>>155907069
I mean ABE and BAD.

>>155907087
The base angles are equal, so we can assume that it is an isosceles trapezoid. Any isosceles trapezoid has its opposite bases parallel.

>>155905047
It's 70. Not to scale and I'm pretty sure you can't use trigonometry if you wanted to cause there's no lengths.

>>155907344
The answer is 20.

>>155906385
Yeah, I had the feeling it was one of those unsolvable meme images

>>155907485
https://www.duckware.com/tech/worldshardesteasygeometryproblem.html
its basically a pain in the ass to solve on a computer since you need to write new triangles into it.

>>155907263
Equal base angles means the overall triangle ABC is isosceles. But I don't think DE is parallel to the base, since its endpoints are being partly defined by AE and BD, which have different angles (60 and 70) relative to base AB. If DE were parallel, those angles would be equal too.

>>155907069
This can't be a perfect trapezoid, its diagonals are not the same. In fact, we don't even know whether it's a trapezoid, nothing indicates that DE is parallel to AB.

>>155905047
Not enough information to answer I think. You'd need to know if either line AB and DE are parallel, be told that triangle CDE is isosceles, or be given angles CDE or CED to be able to complete it.

>>155905047
Not enough info on mid triangle ED to solve without making assumptions.

Is that a real page from the manga, OP?

File: 30b913e9b5cdb4968dd29c35e0114fd1.png (663KB, 972x842px) Image search: [Google]

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>It's impossible

Kuro has a message for you all.

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2nd try. Still, that went nowhere.

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As far as my tired self can think I belive there should only be 1 set of numbers that can solve both the ABED quadrilateral and EDC triangle properly so it should be simple guess and check at this point

>>155908107
That doesn't mean we can assume angle CED or CDE and derive alpha from that. Unless we're given more information about line DE it's unsolvable.

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What was I trying to do again?

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>implying

Straight lines are always 180.

The answer is 90.

>>155908443
>>155908107

Meant to reply to >>155908286

>>155908443
>>155908470
Yes straight lines are always 180, so we know that AEC is 150 and BDC is 140. You can't just assign a value to CED a CDE willy nilly because of that though. There isn't enough information to proceed.

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Still getting nowhere.

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it's not possible we are missing one value. With simple trigonometry this is as far as you'll get you would need trigonometry to find out the answer as >>155908605 states you can't assing a value out of a hat.
source I took all calculus classes

>>155908605
Then how about this?

Simply knowing that BED is 120 means that we also know that EDB is 40, which means that the alpha is 90.

>>155908676
you are assuming values my friend

>>155908676
We don't know that BED is 120 though.

>>155908670
yep thats as far as i got. There just isn't enough info.

>>155908735

see

>>155908107

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>>155905047
>>155903291

Why do we need two of the same thread?

>>155908758
that answer you linked to is incorrect a the total sum of the angles of a trapezoid is 360 by summing the angles in whoever made that it gives 380 which is erroneous
angle of trapezoids would be
ABE = 80
BAD=80
BED= UNKNOWN
EDA=UNKNOWN
but according to this guy >>155908107
BED is 120 and BDA is 100 so if we go by that
80+80+100+120 = 380 and that my fellow anon is incorrect

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>>155908758
Pic related is the furthest you can get as far as numerical values are concerned. What it looks like you did was subtract 30 (BEA) from 150 to get BED, even though you you already got the value of 150 by subtracting 30 (again, BEA) from the 180 degree angle of line BC. There's only one angle BEA there anon, not two.

>>155908889
Yes, you are entire right about this.

This was a really shitty error on my side.

putting an anime girl on it doesnt magically make it /a/ related

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180-60-70=50
180-20-70=90
180-20-90=70
180-80-60=40
180-80-80=20
180-10-40=130
180-20-20=140
360-130-50-70=110
I'm stuck.

>>155909236
It's not solvable without trig.

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>>155909236
Wait am I allowed to do this?

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>>155909286
It's possible with a protractor :^)

>>155909310
There is so much wrong with this it's not even funny

>>155909310
No because those angles aren't 90 degrees you autist.

Look at my image >>155909321 it actually has correct angles visually.

>>155909337
>>155909345
Doh.

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you literally should specify which ones are triangles because abc is not a triangle

>>155906927
This, it's almost as if these kiddies never went through geometry

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Solution: Rape the loli

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I did it boys thread over

>>155909450
Actually I might have fucked something up because of all the numbers

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>>155905047

>>155909478
Is that an envelope?

>>155909498
Yes.

>>155909478
this is nice and all but also wrong you can't just make yourself another triangle and give them the angles you want

>>155909478
Oh nice so >>155909450 was correct and I wasn't full retard.

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Alright I tried to get the angles as close as possible, but this is what the figure should look like.

If you want I can give you the answer by cheating, but it's two scalene triangles next to each other which makes it impossible to solve.

>>155909478
>>155909526
Can one of you try this?

I've forgotten so much in the past 5 years. I'm a failure.

>>155908902
>>155908652
So, now we go algebra. Take the 4 angles we don't know yet as variables and see in which ways we can calculate them. I propose AEC (a,y), BED (a,x), CED (y,z) and BDC (x,z). 4 equations and 4 variables, elementsry school material.

>>155909478
Cheater, can confirm that alpha = 20.

Congratulations, you aren't stupid!

>>155909562
I did tried it based on simple geometry and it can't be done
>>155908889
>>155908670
these are me. you can find them answer but as I previously explain not with simple geometry

Its an undetermined system. You have more variables than equations. At least thats what I got.

>>155909526
I take it you don't understand the inset section. Let me elaborate.

1. ∠GFC = ∠EFA
This much is obvious.

2. ∠FCG = ∠FAE = 10º
By construction of F, ∠GAE = 10º. However because ∠GBF is 20º, and triangle ABC is isosceles, this means that G precisely bisects the angle at the vertex C. Hence ∠FCG is half the angle at vertex C (i.e. half of 20º).

3. ∠CGF = ∠AEF = 30º.
∠CGF = ∠AEF because we have already shown that the other two angles in their respectively triangles (CGF and AEF) are precisely the same. Because ∠AEF is 30º, we also have ∠CGF = 30º.

>>155909478
how do you determine triangle GFD is equilateral?

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>>155909602
>>155909550
>>155909478

Proof of my cheating and that 20 is the winrar.

I can't believe you guys are still saying it's impossible even though >>155907505 found the question with the answer.

>>155909702
that would be correct if it was a 1:1 scale which is not. you took a non-scaled geometry figure and scaled to a perfect figured and from your own drawing approximate the angle.

>>155909716
he drew an imaginary line at a 10 degree angle clockwise from the 10 degree angle, adding up to 20 degrees and making the 70 degree angle 60 degrees. 2 60 degree angles with one unknown add up to an equilateral triangle

I'm not dumb ok. This is stupid. I'm in Calculus. This is bullshit.

>>155909781
30 degrees then?

>>155909716
∠FGD = 60º because ∠FGD = ∠AGB. Because G sits on the axis of symmetry of triangle ACB, the line segments DG and FG must be equal and triangle DGF is isosceles. Since DGF is isosceles with one angle equal to 60º, the other two angles must also be 60º and hence triangle DGF is equilateral.

>>155906927
The diagram is still massively inaccurate and pointlessly misleading.

>>155909810
>>155909838
Oh, duh. Thank you. Very nice.

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>>155909562
>>155909630
I mean like by giving it different angles, then trying to draw the triangle.

>>155909807
There is no approximation involved. F is simply defined as the point on the segment EB such that the angle subtended by EF at A is 10º.

>>155909848
Damn right, and my school did that shit in tests to stop anyone from guessing and make them focus on the equation

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>>155909562
>>155909630
Try drawing the reverse as well.

>>155909450
>>155909478
>>155909550
>>155909761
Protractor anons, you there?
>>155909909
>>155909990

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>>155909990
Good job there

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>>155909807
Scale has nothing to do with it.
Any arbitrary line parallel to the base of a triangle results in a similar triangle.

>>155910218
we're solving for alpha not x you imbecile

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>Using graphic methods
>Not superior linear algebra

>>155910301
Shut up
I was too busy trying to think of a way to make a "Wah! What are we going to do on ∠BED?" joke to copypaste the character for alpha

>>155906415
How do you arrive to the conclusion that both of the triangles in step one are 50 degrees?

>>155910381
If you actually tried solving this system you'll find that you have a free variable.

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>>155905047
The answer is 10 but my teacher would probably mark me anyway for not doing the whole thing, like I was bullshitting or anything. Not that i'm lazy but the answer is literally in front of my face.

>>155910653
It's 20...

>>155907505
I remember seeing this problem a while ago, it's something that nobody would solve the first time they saw it unless they were explicitly told that there was a constant solution.

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I solved it with trigonometry and got approximately 21 degrees.

>>155911383
Cheater!

>>155909526
>>155909807
>jokes on you, I was only pretending to be retarded

>>155911442
I tried solving it without but couldn't, and once I start a math problem I feel like I need to finish it before I can relax.

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>>155910541
Two straight lines in different directions will produce four angles with the opposite angles being equal to each other.
So you have:
angle a = < 90 but < 0
angle b = < 90 but < 0
angle c = > 90 but < 180
angle c = > 90 but < 180
Because all circles equal 360 and a straight line = 180, the sum of angle a and c will equal 180, the sum of angle a and d will equal 180, the sum of angle c and b will equal 180, and the sum of b and d will equal 180.

>>155906793
>acute angles
Yes, Kuro has cute ankles.

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You all make this way to complicated.

>>155910381
Without knowing the relationship between alpha and beta the system has no solution.

>>155909478
winrar. fucking nice.

>>155909478
>tfw to intelligent for /a/

>>155909478
How do you know CG bisects angle ACB?

>>155915372
Because use your eyes and you can tell

>>155915372
CG bisects ∠ACB because segments AG and GB are equal (triangle AGB is isosceles).

>>155915372
You create DF parallel to AB, then G can only be right in the middle

>>155912946
just looking at it 5 seconds I already see multiple mistakes

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For posterity's sake I am uploading a version of the OP image where the angles are not blatantly out of whack, so you don't get 50+ posts complaining about the diagram.

>>155915372
Because triangles ACG and BCG are congruent triangles due to SSS congruence. so ACG and BCG are equal and hence CG bisects ACB.

>>155909478
>>155915661
>>155916025
Thanks to you guys I'll never forget this problem again. Thank you

So what now? Does this mean we can finally fuck Kuro?

>>155916333
You always could, she's short and light, just pick her up and place her over a desk.

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>>155905047
>Triangle is 180 degree
>Obtuse angle in the top left triangle is supposedly 50 degrees, not only making it the smallest angle despite the other 2 being Obtuse, but it's also below 90 degrees.

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>>155917255
>despite the other 2 being Obtuse
acute*

>>155916002
gay amount of effort on your part

Using what set of axioms?

>>155920011
Get out of here ideologist.

>>155920288
No that was a good question.

>>155905047
I am sad this lasted longer than the can do math thread.

>>155905047
Can't be solved without EDC.

>>155923554
Two angles are 80° in the outermost triangle.

>>155907069
It would only be a perfect trapezoid if BE = AD and you can't assume that.

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>>155924586
I don't see it. This is as far as I can get.

This is impossible without using a goddamn protractor.

Is this possible without "cheating" your way through by using exact measurements and adding triangles?

>>155905047
>>155905474
>>155906415
>>155906893

nope. you guys are wrong.

it's 20. the trick to this question is the origional is NOT drawn to scale. If you draw this to scale (there is enough info to do it) the angle comes out to 20.

in fact there is NO way to discover this with MATH. you can only discover this with a protractor.

>>155925835
The angles aren't at scale so it would be useless.

>>155926043
You can discover it with math:
>>155907505 gives a link to a solution that works

>>155906385
I reached to 3 equations but they are insolvable, you're right, there's no solution

Is it 20 ?

>>155925468
Well, triangle BDC is isosceles, maybe that helps

>>155926117
>You can discover it with math
ok, you proved me wrong. just walked through it as described. Its not what I'd call "simple" geometry, but it is solvable with math.

the answer as I said in >>155926043 is still 20 though.

>>155926714
yep, it's 20

>>155926591
check out this post, >>155907505 he links you to the solution with math. I did it with a protractor. took 3 minutes with a protractor, compass and ruler. That is the easiest solution, the math solution works too.

>>155926854
it doesen't help because we can't use trigonometry :)
but even if we could, we must know DEC or EDB to find alpha, and there's no way to find one's without the other's

Fuck off /a/ with your math

>>155927472
>we can't use trigonometry
What sense does that make?

>>155930115
It's the whole point of the puzzle.

>>155931372
But it can't be done otherwise.

>>155925468
70+10 = 60+20

So AC and BC are equally long.

>>155905047
what is the difference between basic trigonometry and elementary geometry?

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>>155907505
It can be done with basic geometry, but even for me it took a few moments of thinking, and I'm in engineering student.
>Pic is the solution.

>>155936065
They are asking for an exact solution you dunce.

>>155936325
>>IQ under 50
The solution is 20 you moron, I wrote it at the bottom of the table (180=>20).
180 mean flat angle=> it is actually an triangle=>meaning a=20

>>155936481
I thought that was a 10. Your mouse handwriting sucks ass.

>>155912946
It doesn't say that AB and DE lines are parallel so you can't do this.

>>155936554
Well duh, it's paint with a mouse. That and that 20 looked more legible when zoomed in on my screen, so I didn't see it to make it better.

>>155910653
you're literally bullshitting and your teacher is right to mark you, you stupid piece of shit

I'm always surprised at how good /a/ is at maths. Especially considering most of us are autists

>>155937078
I doubt more than a 10% of /a/ is actually on the spectrum.

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I don't understand a single thing any of you nerds are talking about.

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Illya thread?

So how exactly would you use trig for this?
Wouldn't you need at least one length?
Or would you just make up a length AB and work from there since in the end that shouldn't effect the answer?

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>>155937177
Study these
https://www.khanacademy.org/math/basic-geo/basic-geo-lines
https://www.khanacademy.org/math/basic-geo/basic-geo-angle
https://www.khanacademy.org/math/basic-geo/basic-geometry-shapes
https://www.khanacademy.org/math/basic-geo/basic-geometry-pythagorean-theorem
https://www.khanacademy.org/math/geometry-home/triangle-properties
https://www.khanacademy.org/math/basic-geo/basic-geo-transformations-congruence

It's quite fun, probably not like you were taught at middle school. You will learn the WHY of things so if nothing made sense when you were learning this at school it will do now. Going through those topics shouldn't even take more than a month. It's never too late to learn.

>>155905047
75, and the angles look wrong visually.

>>155937389
I have not taken trigonometry but I imagine they would solve in terms of radians and convert to angles.

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>>155936065
I made a small error, 30 instead of 20 there. Strange enough, it doesn't affect the outcome.

Now, about this exercise before I go to sleep: It's stupid, it can be solved by basic geometry, but they way you have get there is retarded, and also if someone was to test the angles they would see that they break over each others propreties. And the drawing is deliberate to confuse you.

Solvable, but still retarded.

>>155937078
>good
Most people got it wrong

>>155937599
Why is ExD 180 degrees when BxA must be 50 degrees?

>>155937481
>telling retards to learn
what's next, telling autist to go out and socialize? be reasonable anon
ps. i'm jk, don't take it personally

>>155937561
The angles are visually wrong.
Because you're supposed to solve it with math, not measuring.
Even though redrawing the whole thing to proper scale and then measuring is faster.

>>155937695
You're always the one who ruins the joke for everyone, aren't you.

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>>155909447

>>155937678
i think it was 130 degree, but yeah with god awful as fuck writing it came off as 180

>>155937891
Same question. That angle being 130 degrees makes no sense.

>>155937891
actually scratch that that pic has so many misinformation its fucking pointless to try and digest
you're better off doing it yourself i think

>>155937678
A quadrilater (or how the fuck you spell polygon with 4 margin in english) has an 360 degrees sum of angles. 20+20(including a)+140=180, 160-180=180 remain=> it's a triangle.

I think I fucked up some calculus somewhere considering I did all of it in memory, but I don't feel redrawing all that shit now. Even with how wrong the original drawing is, E can't be 50 total.

>>155938285
How can one side of a triangle be 180º?

>>155938844
man don't even...
i spent good 10 minutes figuring what the fuck does he meant but i cant figure out shit
his problem is not "fucking up some calculus somewhere" or "how wrong the original drawing", it's his fucking brain that is damaged beyond repair

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>>155937877

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Redrawn that shit with some attention to not make errors this time,

>>155938844
A side of a quadrilater not a triangle. A straight line in a triangle has an 180 degree angle

>>155937891
>>155937956
I fucked up some measuments.

>>155912946
This guy was right from the get go with a small caviat. It seems you can change that angle to how it fits your needs, it can be a=65 (70 becomes 65, 60 becomes 65 etc). I can't see some valor to fully fix a as one angle only as long as you adjust the other angles so the blues remain constant.

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>>155905047
The problem actually has multiple answers as the angles given don't determine a unique set of triangles. You can use simple geometry to set up a system of simultaneous equations, then solve them with linear algebra, or rather find out that the equations do not give you a unique solution.

>>155939609
You're not solving the problem correctly, genius.

>>155939684
just because you're too stupid to continue from that pic it does not mean he's not correct baka anon

File: suck my dick kuro.png (32KB, 834x463px) Image search: [Google]

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>>155939684
You can't solve the problem at all, But you can prove that the problem is unsolvable and has infinitely many solutions, with alpha all less than 130. There was a typo in the first picture that I corrected.

>>155939925
Maybe you both retards should read the rules of the puzzle again.

>>155939984
You can solve the problem, you just need to expand the triangle into line segments.

I've honestly forgotten everything past arithmetic

>>155940145
What would dishonestly forgetting things like?

>>155905047
Not this shit thread again.
What does that make, like 5 times?

>>155939609
Ok, so we give alpha a value somewhere in the middle of your allowed range.

Now if we increase it a bit, either the point D must move towards C, E must move towards B, or both.

Since this would change the angle that AE/BD emerge from A/B, which are given form the start, that can't happen. Not without changing the whole outer triangle at least, but that's chance A and B, so that's out as well.

Hell, you could just draw this whole thing and then measure alpha. This will give you one and only one answer.

So while I don't care to figure out what exactly you've fucked up with your little equation system, it's obviously something vital.

a should equal 130, but that's impossible because the angle above a inside of it's triangle is 50 degrees, and that would mean the remaining angle would have to be zero, which it isn't. this bitch is confirmed dumb

>>155940742
Yes, you're dumb.

>>155940367
First time I saw it.

Who fucking cares about triangles? /a/ is more interested in the curves of T H I C C loli hips.

>15 hours since the answer
Well, looks like im a "Little" late.

>>155905047
Good.

>>155943485
Wait where is the answer?

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pretty sure all equations end to a = a so it's impossible

nice way to waste my time at 2 am

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>>155908182
They said that you can't use trygonometry, but we can solve a 3x3 equation system

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>>155905047
>this thread again

>>155905047
can pythagoras solve this?

>>155947764

I think he'd be rolling in his grave.

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Given up, my answer is 60<α<80

>>155948610
Quitter.

>>155948610
Wrong.

File: Geometry3.png (879KB, 2328x2162px) Image search: [Google]

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A = 60

>>155905047
the problem has no unique solutions.
imagine stretching the line AB this will conserve all angles except for the angles around E and D, so those angles can change however much they like and it won't affect the angles on the diagram already.

>>155952720
no you're just bad at basic geometry

This is a kinda famous "easy but fuck you :^)" problem that's been floating around for a while now.

Answer is 20.

>solution posted multiple times
>still anons coming in with wrong answers or claims that it's impossible because they can't read
Fucking hell.
The most hilarious ones are the anons trying to use systems of equations to show that the solution isn't unique. Your systems themselves are incomplete you morons, there's more constraints in there that your dumb ass, and admittedly my own dumb ass, can't find.

>>155909321
>>155909450
>>155909478
>>155909550
>>155909761
Protractor anons?
>>155909909
>>155909990

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>>155905047
>tfw i can do logarithmic equations without aid but i forgot Pythagoras's theorem

>>155905047
70

>>155954247
Maybe because they want to try and solve it themselves first, so they try to do it before reading the thread, then post their own answer, because they might be spoiled with the correct one?

>>155954985
I also did the equation system with the matrix, but before posting my retardedness I had the decency of reading the thread.
Also is not that they got it wrong, but they fucking kept arguing another anon was bullshitting them when they got told they were wrong.

Is Kuro the greatest math teacher of our time?

>>155939984
>alpha can be any value strictly less than 130
False.
0 < alpha < 130
BDE = 130 - alpha
CED = 150 - alpha
CDE = alpha + 10

Though technically, according to the problem, you're not allowed to use linear algebra.