Question

Write in terms of sine and cosine and simplify the expression.

sin^4 A − cos^4 A
cos A − sin A

Answer 1

-cos2A

Answer 2

wrong answer

Answer 3

is it (sina+cosA)(sinA-cosA)

Answer 4

\[\sin^{4} -\cos^{4} =(\sin^{2}+\cos^{2})(\sin^{2}-\cos^{2}) = \sin^{2}-\cos^{2} = -\cos 2A\]