积化和差公式 cosacosB-[cos(@+p)+cos(a-p)] sinsin=-5[cos(a+）-cos(a-p】] cosasin/-][sin(@+B)-sin(@-B)] sinacosB-[sin(@+)+sin(@-B)]( ) ( ) 1 cos cos cos cos 2       = + + −     ( ) ( ) 1 sin sin cos cos 2       = − + − −     ( ) ( ) 1 sin cos sin sin 2       = + + −     ( ) ( ) 1 cos sin sin sin 2       = + − −     积化和差公式