\( \int \frac{1}{e^{2x} - 4e^x + 3} \, dx \)

\( \int \frac{2^x - 1}{e^x} \, dx \quad (SGK chuẩn) \)

\( \int \frac{\cos x}{1 + \cos x} \, dx \)

\( \int \frac{\cos x - \sin x}{\sin x + \cos x} \, dx \)

\( \int \frac{\cos x}{\sin x + \cos x} \, dx = I \)