求(sin8+sin7cos15)\(cos8-sin7sin15)的值

看作：
(sin(15-7)+sin7cos15)(cos(15-7)-sin7sin15)
=(sin(15)cos(7)-cos(15)sin(7)+)+sin7cos15))
cos(15)cos(7)+sin(15)sin(7)-sin7sin15)
=sin(15)cos(7)cos(15)cos(7)
=tan(15)
如果你说的是角度：＝tan(45-30)=(tan45-tan30)/(1+tan45*tan30)=.26795