Đáp án

c) \(\int \sin^4 x \, dx\) 

Đáp án:

• \(\sin^4 x = \left( \frac{1 - \cos 2x}{2} \right)^2 = \frac{1}{4} \left[1  + \cos^2 2x + 2\cos 2x \right]\) 

             \(= \frac{1}{4} \left[1 + \frac{1 + \cos 4x}{2} - 2\cos 2x \right]\) 

            \( = \frac{1}{8} \left( 3 + \cos 4x - 4\cos 2x \right)\)