Question

Evaluate:$\int \sin 7xdx,xϵR.$

Answer 1

$\int \sin 7xdx$

Let $7x=t\Rightarrow 7dx=dt$

$\Rightarrow \int \sin 7xdx=\int \frac{1}{7}\cdot \sin tdt$

$=\frac{-\cos t}{7}=\frac{-\cos 7x}{7}$.