Editor
The value of $\int_{0}^{\frac{\pi}{2}} \cos^{2}xdx$ is:
Difficulty: Easy
A: 
$\frac{\pi}{2}$
B: 
$\frac{\pi}{3}$
C: 
$\frac{\pi}{4}$
D: 
$\frac{-\pi}{3}$