Question

Plz explain me that how is it possible ?

Answer 1

cos x/2 /sin x/2 = cotx/2

Answer 2

I think there is a common mistake to be so casual using a mathmatical formula for cosine (2x)
it is cosine 2x= 2(cosine x)^2 -1
so here the only mistake is in the second par of answer
I.e cot x/2 should be replaced with (cot x/2)^2