CBSE Class 10 Maths (Standard) 2020 · Paper 30/5/1 · Question 23

Introduction to Trigonometry 2 marks Medium

A

B

and

C

are interior angles of a

△ A B C

, then show that

cos (\frac{B + C}{2}) = sin (\frac{A}{2})

Answer

Since

\frac{B + C}{2} = 9 0^{\circ} - \frac{A}{2}

, we have

cos (\frac{B + C}{2}) = sin (\frac{A}{2})

, as required.

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