sin(30°+x)-sin(30°-x)
问题描述：
sin(30°+x)-sin(30°-x)
用和（差）角公式化简
怎么算的
答
sin(a) + sin(b) = 2 * sin((a+b)/2) * cos((a-b)/2)
=> sin(30+x) - sin(30-x)
= sin(30+x) + sin(x-30)
= 2 * sin(x) * cos(30)
= 2 * sin(x) * (3/4)^(1/2)