SOLUTION: Marty is proving that the following trigonometric identity is true: tan^2θ⋅cos^2θ=1−cos^2θ Which step would be the first line of his proof? ta

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Question 1074684: Marty is proving that the following trigonometric identity is true:
tan^2θ⋅cos^2θ=1−cos^2θ

Which step would be the first line of his proof?
tan^2θ⋅cos^2θ=1−sin^2θ
tan^2θ⋅cos^2θ=tan^2θ
tan^2θ⋅cos^2θ=sin^2θ
tan^2θ=1−cos^2θ⋅cos^2θ
Found 2 solutions by Alan3354, ikleyn:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
I would add cos^2 to each side,
--> tan^2 = 1
Not an identity.
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And, I would use parentheses.

Answer by ikleyn(52834) About Me  (Show Source):
You can put this solution on YOUR website!
.
Marty is proving that the following trigonometric identity is true:
tan^2θ⋅cos^2θ=1−cos^2θ

Which step would be the first line of his proof? 

tan^2θ⋅cos^2θ=1−sin^2θ

tan^2θ⋅cos^2θ=tan^2θ

tan^2θ⋅cos^2θ=sin^2θ     <<<---+++ This one.

tan^2θ=1−cos^2θ⋅cos^2θ