∫(1+cosx)9/7(1−cosx)2/7dx=∫(1+cosx)(1+cosx)2/7(1−cosx)2/7dx=∫(1+cosx1−cosx)2/71+cosxdx=∫(2cos22x2sin22x)2/7⋅2cos22xdx=∫(tan22x)2/7⋅21sec22xdx=21∫tan4/72x⋅sec22xdx Let tan2x=t⇒sec22xdx=2dt=∫t4/7dt=74+1t74+1+C=117t11/7+C=117tan11/72x+C