HELP PLEASE! I need to derive an identity from a different identity and I do not know how! Derive: sin^2x+cos^x=1 from cos(x+y)=cosxcosy-sinxsiny using cos(0)=1

asked Feb 17, 2023 136k views

4 votes

HELP PLEASE! I need to derive an identity from a different identity and I do not know how!

Derive:
sin^2x+cos^x=1

from

using cos(0)=1

6.6k points

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3 votes

Answer:

cos(0) = cos(x-x)=cos(x)*(cos-x)-sin(x)*sin(-x)=cos^2(x)-(-sin^2(x)) = sin^2(x)+cos^2(x) = cos(0) = 1

Sarpe answered Feb 24, 2023

by Sarpe

7.2k points

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