sec^2（x/2)/2tan（x/2)等于1/sinx,麻烦高手帮我把详细步骤写出来!

sec^2（x/2)/[2tan（x/2)]
=[1/cos²(x/2)]÷[2sin(x/2)/cos(x/2)]
=[1/cos²(x/2)]×cos(x/2)/[2sin(x/2)]
=1/[2sin(x/2)*cos(x/2)]
=1/sinx

sec^2（x/2)/2tan（x/2)
因为sec(x/2) = 1/cos(x/2)
又因为tan(x/2) = sin(x/2) / cos(x/2)
所以原式 =
cos(x/2)
-----------------------
cos^2(x/2)·2sin(x/2)
= 1/2sin(x/2)cos(x/2) = 1/sinx