Tìm nguyên hàm tích phân (cos 2x / sin^2x cos^2x) dx

\(\int {\frac{{\cos 2x}}{{{{\sin }^2}x{{\cos }^2}x}}dx} \)

\( = \int {\frac{{4\cos 2x}}{{4{{\sin }^2}x{{\cos }^2}x}}dx} \)

\( = \int {\frac{{2.2\cos 2x}}{{{{\left( {\sin 2x} \right)}^2}}}dx} \)

\( = \int {\frac{2}{{{{\left( {\sin 2x} \right)}^2}}}d\left( {\sin 2x} \right)} \)

\( = \frac{{ - 2}}{{\sin 2x}} + C\).