Question

sin（x+a）-sinx=2cos(（x+(a/2))sin(a/2)怎么看的,没分了,来回答的谢谢

Answer 1

左边=sin[(x+a/2)+a/2]-sin[(x+a/2)-a/2]

=[sin(x+a/2)cosa/2+cos(x+a/2)sina/2]-[sin(x+a/2)cosa/2-cos(x+a/2)sina/2]

=2cos(x+a/2)sina/2