Question

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Answer 1

Correct Question,

If A,B and C are the angles in a triangle,then prove that sin(B+C)/2= CosA/2

Solution:

To prove: sin(B+C)/2=cosA/2

Proof:

By Angle Sum Property of a triangle,

A+B+C=180

→B+C=180-A

Dividing both sides by 2,

→(B+C)/2=90-A/2

Multiplying both sides by sin function,

→sin(B+C)/2=sin(90-A/2)

We know that,

sin(90-∅)=cos∅

Thus,

→sin(B+C)/2=cosA/2

Hence,proved