为什么tan(x/2)为啥=(1-cosx/sinx)

问题描述:


为什么tan(x/2)为啥=(1-cosx/sinx)

解tanx/2
=(sinx/2)/(cosx/2)
=2(sinx/2)^2/2(sinx/2)(cosx/2)
=2(sinx/2)^2/sinx
=(1-cosx)/sinx.(注意2sin^(x/2)=1-cosx)