Sint/(1-cost)是如何得于Cot(t/2)的?中间有个小错误是1-cos2a=[1-(1-2Sin^2a)].

分类: 作业答案 • 2022-04-18 15:00:41

问题描述：

Sint/(1-cost)是如何得于Cot(t/2)的?
中间有个小错误是1-cos2a=[1-(1-2Sin^2a)].

答

令t=2a
a=t/2
则原式=sin2a/(1-cos2a)
=2sinacosa/[1-(1-2sin²a)]
=2sinacosa/2sin²a
=cosa/sina
=cota
=cot(t/2)