up. In a triangle ABC, write cosä˝2C):15. In a triangle ABC, write – InterviewSolution

1.

up. In a triangle ABC, write cosä˝2C):15. In a triangle ABC, write cosB+C interms of angle A.ICBSE 2016]

Answer»

We know in a triangle ,

A + B + C = 180

B + C = 180° - A

(B+C)/2 = 90° - A/2

So,

cos ( B+ C)/2

Cos ( 90 - A/2)

sin ( A/2)

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