UV আকারের (Integration by parts)

sin4xsin2xdx=?\int \sin 4 x \sin 2 x d x \quad = ?

Solve:

sin4xsin2xdx=12{cos(4x2x)cos(4x+2x)}dx=12(cos2xcos6x)dx=12(sin2x2sin6x6)+c=14sin2x112sin6x+c \begin{array}{l} \int \sin 4 x \sin 2 x d x \quad \\ =\int \frac{1}{2}\{\cos (4 x-2 x)-\cos (4 x+2 x)\} d x \\ =\frac{1}{2} \int(\cos 2 x-\cos 6 x) d x \\ =\frac{1}{2}\left(\frac{\sin 2 x}{2}-\frac{\sin 6 x}{6}\right)+c \\ =\frac{1}{4} \sin 2 x-\frac{1}{12} \sin 6 x+c \end{array}

UV আকারের (Integration by parts) টপিকের ওপরে পরীক্ষা দাও