代入积分上下限，求得原积分=-6π^2
=∫t²sint-2tsin²t+sin³tdt=-∫t²dcost-∫t(1-cos2t)dt+∫(-π到π)sin³tdt=-t²cost+∫costdt²-t²/2+1/2∫tdsin2t+0=-4π²+2∫tdsint-2π²+tsin2t/2-1/2∫sin2tdt=-6π²+2tsint-2∫sintdt+0+cos2t/4=-6π²
