sin2x等于多少?
问题描述:
sin2x等于多少?
答
sin2x=2sinxcosx,这其实是由两角和的正弦公式sin(x+y)=sinxcosy+cosxsiny 得到.此外,还有几个三角恒等式:cos(x+y)=cosxcosy-sinxsinycos(x-y)=cosxcosy+sinxsinysin(x-y)=sinxcosy-cosxsiny tan(x+y)=(t...