If tanA + tanB =A And CotA + CotB =B, prove that: cot(A +B) = 1/a – 1/b.
Given tanA + tanB =A And cotA + cotB =B
Consider cotA + cotB =B
Then,
RHS 
We know that 
= cot(A +B) = LHS
Hence, proved.
23
If tanA + tanB =A And CotA + CotB =B, prove that: cot(A +B) = 1/a – 1/b.
Given tanA + tanB =A And cotA + cotB =B
Consider cotA + cotB =B
Then,
RHS
We know that
= cot(A +B) = LHS
Hence, proved.