Proving expressions in Trigonometry

this expression is wrong.

to check this, simply put A=B = 45^o

LHS =  (1-cos45^o +cos90^o) / (1+cos45^o +cos90^o) = (2-1) / (2+1)

RHS = tan (45^o/2) cot (45^o/2) =1

since LHS RHS

i.e. this cant be proved.