SOLUTION: Prove each identity: c) cos^2θ=(1-sinθ)(1+sinθ) d) sin^2θ+2cos^2θ-1=cos^2θ e) sin^4θ - cos^4θ =sin^2θ -cos^2θ g) 1-c

Algebra ->  Trigonometry-basics -> SOLUTION: Prove each identity: c) cos^2θ=(1-sinθ)(1+sinθ) d) sin^2θ+2cos^2θ-1=cos^2θ e) sin^4θ - cos^4θ =sin^2θ -cos^2θ g) 1-c      Log On


   

Question 939398: Prove each identity:
c) cos^2θ=(1-sinθ)(1+sinθ)
d) sin^2θ+2cos^2θ-1=cos^2θ
e) sin^4θ - cos^4θ =sin^2θ -cos^2θ
g) 1-cos^2x=sinxcosx/cotx
Thanks :)
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
Prove each identity:
c) cos^2θ=(1-sinθ)(1+sinθ)
(1-sinθ)(1+sinθ)=1-sin^2θ=cos^2θ
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d) sin^2θ+2cos^2θ-1=cos^2θ
1-cos^2θ+2cos^2θ-1=cos^2θ
..
e) sin^4θ - cos^4θ =sin^2θ -cos^2θ
I don't think this problem is written correctly
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g) 1-cos^2x=sinxcosx/cotx
sinxcosx/cotx=sinxcosx/(cosx/sinx)=sin^2x=1-cos^2x