sin10°sin50°-sin50°sin70°-sin70°sin10°=?请给出过程,谢谢了谢谢!
网友回答
=sin10sin50-sin70sin10-sin50sin70
=sin10{sin(60-10)-sin(60+10)}-sin(60-10)sin(60+10)
=sin10(-2sin10*cos60)-sin60*sin60cos10*cos10+sin10*sin10cos60*cos60
=-sin10*sin10-3/4+sin10*sin10
=-3/4======以下答案可供参考======
供参考答案1:
把这三个乘积都用积化和差公式就可以解决