举报
杭州的马丁
sin^2a+sin^2b+2sina*sinb*cos(a+b)
=sin^2a+sin^2b+2sina*sinb*(cosacosb-sinasinb)
=(1-cos2a)/2+(1-cos2b)/2+sin2asin2b /2-(1-cos2a)(1-cos2b)/2
=(1+sin2asin2b-cos2acos2b)/2
=【1- cos2(a+b )】/2
=sin∧2(a+b)
最后一步公式为
Cos2A=1—2sin^2 A的转化
刚才丢了点东西,算错了
抱歉,刚才有点事没来得及给你答案