Question

\[\int_{0}^{\pi/2} cos^{2}\theta d\theta\]

Answer 1

use this formula
\[\cos^2 \theta=\frac{1+\cos 2 \theta}{2}\]

Answer 2

why can't I just say \[\frac 1 3 cos^3 \theta\]? or is that illegal?

Answer 3

that is illegal
because
\[\frac{d}{d \theta} (\frac{1}{3} \cos^3 \theta)= -\sin \theta \ \cos^2 \theta\]

Answer 4

true...thanks

Answer 5

yw