已知tanθ怎么求sinθ/2和cosθ/2?tanθ=sinθ/cosθsin2θ=2sinθcosθ就是sinθ=2sinθ/2cosθ/2cos2θ=2(cosθ)^2-1=1-2(sinθ)^2就是cosθ=2(cosθ/2)^2-1=1-2(sinθ/2)^2带入即可tanθ=sinθ/cosθ=【2sinθ/2cosθ/2】/【2(cosθ/2)^2-1】这下把它带进去就行了这总知道了吧~~O(∩_∩)O哈哈~回答完毕~望采纳~O(∩_∩)O谢谢