微积分学/不定积分/半角代換法

$\begin{matrix} u = \tan \frac{x}{2} \sin x = \frac{2 u}{1 + u^{2}} \cos x = \frac{1 - u^{2}}{1 + u^{2}} \\ d x = \frac{2}{1 + u^{2}} d u \tan x = \frac{2 u}{1 - u^{2}} \\ \tan (α \pm β) = \frac{\tan α \pm \tan β}{1 \mp \tan α \tan β} \end{matrix}$ Template:See also