Question #c38f4

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Answer 1 · 2016-10-24T22:35:40

Substitute in $cos^2(x) = 1-sin^2(x)$ .

Using the identity

$sin^2(x) + cos^2(x) = 1$

we can subtract $sin^2(x)$ from both sides to obtain

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

With that:

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

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