题目

∫sint*sinwtdt怎么求积分?还有∫cost*coswtdt?

提问时间：2021-02-25

答案

用积化和差公式：sinxsiny=(1/2)[cos[(x-y)-cos(x+y)],cosxcosy=(1/2)[cos(x+y)+cos(x-y)]∫sint*sinωt dt= (1/2)∫cos(t-ωt) dt - (1/2)∫cos(t+ωt) dt= (1/2)∫cos(1-ω)t dt - (1/2)∫cos(1+ω)t dt= (1/2)/(1...