Factor and simplify: 1-2sin²x + sin^4x

Question

Possible answers... a. sin^2 x   b. (1-sin^2 x)   c. cos^4 x   d. (1+tan^2 x)

Answer 1

=(1 - sin²x)²   so it's (cos²x)² using factoring a perfect square and the Pythagorean identity.  Answer: c