Tan(a+b)=x &tan(a-b)=y find the values of tan2a &tan 2b?

Write,
tan 2a = tan [ (a+b) + (a-b)]
= [tan (a+b) + tan (a-b)]/ [1- tan(a+b).tan(a-b)]

now, put the reqd values and find tan 2a. Similarly, write, tan 2b = tan[ (a+b) - (a-b)] and apply d formula. Substitute and get d value.