Question

In ∆ABC, a cos (B – C) + b cos (C – A) + c cos (A – B) (where a, b, c are sides of ∆) equals

• A.
• B. $\frac { \mathrm { abc } } { 4 \mathrm { R } ^ { 2 } }$
• C. $\frac { 4 a b c } { R ^ { 2 } }$
• D. None

Answer 1

Answer: (A)

Answer 2

a = 2R sin A

b = 2R sin B

& c = 2R sin C