Evaluate:

$\int \sin 3x\sin xdx$

Evaluate:

$\int \frac{x{e}^x}{(x+1{)}^2}dx$

Evaluate:

$\int e^x\left\{\tan x-\log \cos x\right\}dx$

Evaluate:

$\int \frac{dx}{(1-\sin x)}$

Evaluate:

$\int x\cos x^{2}dx$

Evaluate:

$\int \frac{\cot x}{\sqrt{\sin x}}dx$

Evaluate:

$\int \frac{{\sec }^{2}x}{{cosec}^{2}x}dx$

Evaluate:

$\int {\sin }^{-1}\left(\cos x\right)dx$

Evaluate:

$\int \frac{dx}{(\sqrt{x+2}+\sqrt{x+1})}$