I didn't get any help all the previous times, can s/o help me at this at least?
Prove that sin^2x+cos^2x=1
Please don't give me any links; explain!!!!

Question

I didn't get any help all the previous times, can s/o help me at this at least?
Prove that sin^2x+cos^2x=1
Please don't give me any links; explain!!!!

amistre64 · Answer

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amistre64 · Answer

by definitions:

sinx = b/r;  b = r sinx

cosx = a/r;  a = r cosx

by pythag thrm

a^2 + b^2 = r^2

substitute and simplify

perl · Answer

@amistre64  so let r = 1 ?

amistre64 · Answer

letting r=1 is not general enough

solomonzelman · Answer

Guys guys I am trying to get SAT practice questions.... PLEASE  !!!
I was like dude, learn how to read please...(Sorry I had to say that....

perl · Answer

@amistre64 
ok i see what you did, very nice argument.
you can also do the following. let x = theta, then use definition of sin theta and cos theta using a unit cirlce

nincompoop · Answer

it's the same

perl · Answer

right, its similar. draw a circle with radius r

solomonzelman · Answer

what?!
All right I am out

I have to ace the English test and come back here

Good buy!!

nincompoop · Answer

that's about the most straight-forward proof, @SolomonZelman

perl · Answer

you can draw a circle with radius 1, that will work too

perl · Answer

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