Example-12. If A, B and C are interior angles of triangle ABC, then show thatv
B+C /2 = cos a/2
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A+B+C=180
B+C=180-c
Divinding both sides by 2
B+C/2=180-C/2
Putting sin on both sides
Sin(B+C/2)=sin (90-C/2)
(CosA=sin(90-A)
Sin(B+C/2)=cosA/2
B+C=180-c
Divinding both sides by 2
B+C/2=180-C/2
Putting sin on both sides
Sin(B+C/2)=sin (90-C/2)
(CosA=sin(90-A)
Sin(B+C/2)=cosA/2
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