How does a vector table help us get the length of a a vector

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>>8689735
Here's the vector table I made for it. I don't get how I obtain the length of the vector in question and the value of the angle theta from this information. I get the sum of the x and y components of the other vectors in the table are the x and y components of the vector in question, but where do I go from there. How does this help me find its length and theta?

>>8689735
Halp

Sum of all y components = 0
Sum of all x components = 0

Create a system of equations using this and solve for D and theta

>>8689735
Wtf is a vector table? This guy is a moron, I think. The vector you're trying to find is the sum of all others, except it's drawn wrong. The tail
Should be point out from th origin.

Add all the other vectors in component form, I.e.

500cos(200)i + 500sin)200 + etc.

Good luck. I knew you must've been at a CC and confirmed it with google because I had to suffer through a similar dumbed down physics for engineers class, taught by a monkey like yours, who shouldn't even be teaching hs physics, let alone calculus based physics.

>>8689823
>>8689833

Ah thanks guys I get it now. Yeah just transferred here from my local state uni. Wish I had earlier cuz it's significantly dumbed down.

>>8689833
Wait sorry, when you say add all the other vectors in component form, isn't that what I did here
>>8689745

My main issue with the prof is he goes way too fast with too little explanation

>>8689745
You seem to be applying the trig formulae correctly but you are making sign errors by forgetting that vectors have a direction, for example it should be -500cos(20), +700sin(45) and 1000sin(10) because they are travelling in the negative x, positive y and positive y directions respectively. The way you should notate this is in vector form as such. [eqn]\begin{pmatrix}1000cos(10)\\1000sin(10)\end{pmatrix}+\begin{pmatrix}-700cos(45)\\700sin(45)\end{pmatrix}+\begin{pmatrix}-500cos(20)\\-500sin(20)\end{pmatrix}+\begin{pmatrix}-Dcos(10)\\-Dsin(10)\end{pmatrix}=\begin{pmatrix}0\\0\end{pmatrix}[/eqn]. It should be intuitive where to solve from this point

>>8690065
[math]\begin{pmatrix}1000cos(10)\\1000sin(10)\end{pmatrix}+\begin{pmatrix}-700cos(45)\\700sin(45)\end{pmatrix}+\begin{pmatrix}-500cos(20)\\-500sin(20)\end{pmatrix}+\begin{pmatrix}-Dcos(10)\\-Dsin(10)\end{pmatrix}=\begin{pmatrix}0\\0\end{pmatrix}[/math]
Didn't notice eqn doesn't work

>>8689963
I didn't look at your work, sorry. The length is the magnitude of the resulting vector you find and the theta is arctan (y/x), where y is your scalar on j and x your scalar on i

>>8690234
That's what I don't understand, I've added the x and y components, but what is the resulting vector? (D) I get that theta is ry/rx. What do you mean by the scalar on j and I? What are you referring to as J and I?

>>8690990
i and j are the unit vectors in the x and y direction, respectively.
You added all the components, so now add the components from vector D like this person did >>8690074 and set it equal to zero because it ends at the origin.

You will be left with two equations (one for the x component and one for the y component) and two unknowns (the magnitude of D and the angle theta). Then it is trivial to solve.

>>8691012
Gotcha. Thanks