\( \int \left( \frac{\sin x - \cos x}{\sin x + \cos x} \right)^2 \, dx \)

Đáp án:

•  \( \int \left( \frac{\sin x - \cos x}{\sin x + \cos x} \right)^2 \, dx = \int \tan^2 \left( x - \frac{\pi}{4} \right) \, dx \quad\) Đặt\( \, t = x - \frac{\pi}{4} \)