Tìm nguyên hàm: J=∫(cos3x.cos4x+sin^3 2x)dx

A. $\frac{1}{14}\sin 7x-\frac{1}{2}\sin x-\frac{3}{8}\cos 2x+\frac{1}{24}\cos 6x+C$

B. $\frac{1}{14}\sin 7x+\frac{1}{2}\sin x+\frac{3}{8}\cos 2x+\frac{1}{24}\cos 6x+C$

C. $\frac{1}{14}\sin 7x+\frac{1}{2}\sin x-\frac{3}{8}\cos 2x+\frac{1}{24}\cos 6x+C$

D. $\frac{1}{14}\sin 7x+\frac{1}{2}\sin x-\frac{3}{8}\cos 2x-2\frac{1}{24}\cos 6x+C$