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)]._数学解答

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)].

人气：117 ℃　时间：2020-09-10 03:12:57

解答

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