Precalculus
posted by Anonymous .
I don't understand how rationalizing the numerator of tan(1/2)x=sin x/(1+cos x) results tan(1/2)x=(1cos x)/sin x. The question is what do you multiply by to the first equation to get the second.

[sin x/(1+cos x)] [ [1cos x)/(1cos x) ]
= sin x (1cos x) /(1  cos^2 x)
BUT
1  cos^2 x = sin^2 x
get it?