Question

Which of the following are identities? Check all that apply. A. cot2x + 1 = csc2x B. tan2x = 1 - sec2x C. sin2x = 1 + cos2x D. sin2x + cos2x = 1

Answer 1

Answer: A. Cot^2 x+1 =csc^2 x

& D. Sin^2 x+Cos^2 x=1

Step-by-step explanation:

A P E X approved.

Answer 2

I'll assume those are squares. We know D is an identity:


`\sin^2 x + \cos ^2 x = 1`

Dividing through by
`\sin ^2 x`


`1 + \cot^2 x = \csc^2 x`

That's A.

Dividing the original through by
`\cos ^2 x`


`\tan^2 x + 1 = \sec^2 x`

Not quite B, wrong sign on tangent.

C has the wrong sign on cosine squared as well.

Identities: A & D