Question

Three forces vector P, vector Q and vector R  acting along LA , IB and IC, where I is the incentre of a ΔABC, are in equilibrium. Then vector P: vector Q: vector R is 

(a) secA/2 : secB/2 :sec C/2

(b) sinA/2 : sinB/2 : sinC/2

(c) cosA/2 : cosB/2 : cosC/2

(d) cosecA/2 : cosecB/2 : cosecC/2 .

Answer 1

and ∠AIB​ = ​π/2 + C/2.

Now using Lami’s theorem we have