Question

find the value please​

Answer 1

Answer:

Need to know:

• cos x = sin (90° - x)
• sin x = cos (90° - x)

(i)  Since A, B, C are angles in a triangle,  A + B + C = 180°.  So...

sin( (B+C) / 2 ) = sin ( ( 180° - A ) / 2 ) = sin ( 90° - A/2 ) = cos (A/2)

(ii)  B+C = 180° - A = 180° - 90° = 90°

=> (B+C)/2 = 45°

=> tan( (B+C)/2 ) = tan 45° = 1