Question

Evaluate $\int \sin 3xdx$

Answer 1

According to the problem:

subsititute the $u=3x$ and $du=3dx$

Implies that

$\int \sin 3xdx=\int \frac{\sin udu}{3}$

Implies that

$=-\frac{\cos u}{3}$

Implies that

$=-\frac{\cos 3x}{3}+C$