Question

If in a triangle ABC 2cosA/a + cosB/b + 2cosC/c = a/bc + b/ca then the value of the angle is

(A) π/8

(B) π/4

(C) π/3

(D) π/2

Answer 1

Correct option (D) π/2

Explanation:

L.H.S. = 2cosA/a + 2cosB/b + 2cosC/c

by cosine rule

= (2b² + 2c² - 2a² + 2a² + 2c² - 2b² + 2a² + 2b² - 2c²)/2abc

= (a² + b² + c²)/abc = a/bc + b/ca + c/ab = a/bc + b/ca

then we can conclude that there should nor c/ab term in 

L.H.S.. It is possible only if cosA = 0

A = π/2