Question

sec^4 θ - cos^4 θ = 1 - 2cos²θ

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Answer 1

Step-by-step explanation:

We want to show that

sin^4x−cos^4x=1−2cos^2x

We'll work with the LHS:

Using the identity

sin^2x+cos^2x≡1

we get:

(1−cos^2x)^2−cos^4x

1−2cos^2x+cos^4x−cos^4x

1−2cos^2x

LHS=1−2cos^2x

LHS=RHS

i hope answer is correct.