Question

prove that sin a /1+cos a = cot a/2

Answer 1

sin a /(1 + 2cos²a/2 -1)
= 2sin(a/2)cos(a/2 )/(2cos²a/2)
:- 2 and cos a/2 gets cancelled.
so, sin (a/2) / cos(a/2)
= cot (a/2).
Hope it help