求(sin8+sin7cos15)\(cos8-sin7sin15)的值
问题描述：
求(sin8+sin7cos15)\(cos8-sin7sin15)的值
答
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)=(t...