If A + B + C = π, then cos A + cos B – cos C = | MATH - SOLUTION OF TRIGONOMETRICAL EQUATIONS | SolveeIt | Solveeit

Today, November 18

Question

If A + B + C = π, then cos A + cos B – cos C =

A

– 1 + 4 sin A/2 cos B/2 sin C/2

B

– 1 + 4 cos A/2 sin B/2 sin C/2

C

4 cos A/2 sin B/2 sin C/2

D

– 1 + 4 cos A/2 cos B/2 sin C/2

Answer

– 1 + 4 cos A/2 cos B/2 sin C/2

Explanation

Solution

cos A + cos B – cos C

= 2 cos cos –

= – 1 + 2 sin

= – 1 + 2 sin

= – 1 + 4 cos cos sin