u=-(sint+sin 3t+=sin 5t) u=-(sint +sin 3t +=sin 5t +-sin 7t) 3 5sin5 ) 5 1 sin3 3 1 (sin 4 u t + t + t  = sin7 ) 7 1 sin5 5 1 sin3 3 1 (sin 4 u t + t + t + t  =