Use the appropriate sum or difference identity to write the given expression as a function of x alone.
-cos (90° + x)
A) -sin x
B) cos x
C) -cos x
D) sin x

Question

Quizplus · Accepted Answer

The correct expression using the sum identity for cosine, cos(α + β) = cos α cos β - sin α sin β, with α = 90° and β = x, simplifies to -sin x because cos 90° = 0 and sin 90° = 1.

Use the Appropriate Sum or Difference Identity to Write the Given