Tìm: a) tích phân (3cosx -4sinx) dx ; b) tích phân (1/ cos^2 x -1/ sin^2 x) dx .

a) \(\int {\left( {3\cos x - 4\sin x} \right)dx} \)\( = 3\int {\cos xdx - 4\int {\sin xdx} } \)\( = 3\sin x + 4\cos x + C\).

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