Tìm: a) tích phân (2cosx -3/ sin^2 x) dx b) tích phân 4sin^2 x/2 dx

a) \(\int {\left( {2\cos x - \frac{3}{{{{\sin }^2}x}}} \right)} dx\)\( = 2\int {\cos xdx - 3\int {\frac{1}{{{{\sin }^2}x}}dx} } \)\( = 2\sin x + 3\cot x + C\).

b) \(\int {4{{\sin }^2}} \frac{x}{2}dx\)\( = 2\int {\left( {1 - \cos x} \right)} dx\)\( = 2\int {dx - 2\int {\cos xdx} } \)\( = 2x - 2\sin x + C\).