(a/p) + (b/q) + (c/r) = 2(tanA + tanB + tanC).

where a, b, c are the sides opposite to vertices A, B, C respectively. A, B, C are also the angles made at the respective vertices.

My attempt: I don't know how to calculate and represent p, q, r in the terms of a, b, c and A, B, C to proceed in this question. Please help.