Prove sinA/1+cosA =tan1/2A

did you mean:

sinA/(1+cosA) = tan (1/2)A ?

Let tan (1/2)A = tanx
then we can write our equation as

sin 2x/(1 + cos 2x) = tanx

LS = 2sinxcosx/(sin^x + cos^2x + cos^2x - sin^2x)
= 2 sinxcosx/2cos^2x
= sinx/cosx
= tanx
= RS