Trigonometric Integrals: Some trigonometric integrals can be evaluated by repeated integration by parts, by using trigonometric identities or by using suitable trigonometric identities.
$\int_0^{2\pi} \sin^2x \hbox{d} x =$
$\int \sin^2 x \hbox{d} x =$ $+C$
$\int\frac{1}{\tan x} \hbox{d} x=$ $+C$