7.1 Integration By Parts/43

${\begin{aligned}\int \sin ^{2}(x)dx&=-{\frac {1}{2}}\cos(x)\cdot \sin ^{2-1}x+{\frac {2-1}{2}}\int \sin ^{0}(x)dx\\[2ex]\end{aligned}}$

\int\sin^2(x)dx &= - \frac{1}{2}\cos(x) \cdot \sin^{2-1}x + \frac{2-1}{2} \int\sin^{0}(x)dx \\[2ex]

&= -\frac{1}{2}\cos(x)\sin(x) + \frac{1}{2}x + c \\[2ex] &= -\frac{1}{2} \cdot 2 \cdot \frac{1}{2}\sin(x)\cos(x) + \frac{x}{2} + c \\[2ex] &= -\frac{1}{4}\sin(2x) + \frac{x}{2} + c \\[2ex]