Question

(cosx + 2sinx)^2 + (2cosx - sinx)^2=5

Answer 1

what are the instructions?

Answer 2

this about trigonometric identities and I do not know how to do the problem this

Answer 3

\[(\cos x + 2\sin x)^2 + (2 \cos x- \sin x)^2 = 5\]\[(\cos x + 2\sin x)(\cos x + 2\sin x) + (2\cos x - \sin x)(2\cos x-\sin x) = 5\]Multiply that out and collect like terms. Remember that \[\sin^2 x + \cos^2 x = 1\]