mathematics
posted by diviya .
if sinA+sinB=x and cosAcosB=y then find tan[(AB)/2]

I don't know how many trig ratios of halfangles you have developed or know but here is a page where many of them are done.
http://www.intmath.com/analytictrigonometry/4halfangleformulas.php
about 2/3 of the way down you should find
tan [(A+B)/2) = (sinA +sinB)/(cosA + cosB)
= x/y 
Yo

y/x