Yes, you are on the right track (except that the 6 should be 1/6 — remember that tan = sin/cos, not cos/sin). For the last part, use the formula .
Given that , prove that and deduce a relationship between and . Given further that , calculate the value of .
I have already proved the equation.
I have also tried to deduce the relationship between tanA and tanB,
But am not sure if I am on the right track. Lastly, need help with calculating the value of