Is my calculator wrong?!

learn to read retard

>>8720435
cos^2(x)+sin^2(x)=1

cos^2(x)-1= -sin^2(x)

now substitute

into your trig identity

cos^2(x)-sin^2(x)=cos(2x)

2cos^2(x)-1=cos(2x)

>>8720438
Thank you for the thorough explanation.

>>8720435
Lmao, trying to cheat on your precalc test. Nice.

Besides the fact that you have to be a massive faggot to buy a calculator so you can more effectively cheat, you'll regret not learning your trig identities in calculus.

>>8720452
>cos^2(x)-sin^2(x)=cos(2x)
What trig identity are you using to substitute?

>2cos^2(x)-1=cos(2x)
I still don't understand how you get rid of the -1
I get that 2cos^2(x) = cos^2(2x) , but how does the -1 cancel out?

>>8720435
Are you the middle school brainlet from earlier who dropped out of business to study physics?

>>8720487
nope
>>8720477
>you'll regret not learning your trig identities in calculus.
I'm currently in Calculus now, the reason it says pre-calc at the top of the screen is because I have a tab with all of the identities written out for reference.

I know
cos(2x) = cos^2(x) – sin^2(x) = 1 – 2 sin^2(x) = 2 cos^2(x) – 1
because the double angle identity says so, but I don't understand why how one would come to such a conclusion mathmatically

>>8720510
there is a proof of the double angle identities. its geometric, look it up on khan academy

>>8720483
>I get that 2cos^2(x) = cos^2(2x)

Fuck... I just realized I'm a brainlet

>>8720532
Just did, thanks

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1MB, 2560x1920px

>>8720553

>>8720477
I remember in high school we automatically lost marks on tests if we walked into an exam room without a calculator.

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>>8720575
Thanks mate!