Question

!!!! Which of the following is a step in evaluating: ∫ cos2 5x dx

A. 1+cos 10x/ 2dx
B. 1-cos 10x / 20dx
C. 1+cos 10x / 20dx
D. 1 - cos 10x / 2dx

Answer 1

It follows from the double angle identity for cosine:


`\cos^2(5x)=\frac{1+\cos2(5x)}2=\frac{1+\cos(10x)}2`