\[\tan (A+B) = \frac{tan A + tanB}{1-tanAtanB} \]
tan A tanB \[ \neq \] 1 Otherwise it will give infinite value .
In other words A+B should not be 90.
ex- if A=30 and B = 60 then this formula will result infinite output.
and so with any set of complementary angle like A=45 B=45 OR A=20 B=70
