If A,B and C are interior angles of triangle ABC,then show that cos(B+

1.	If A,B and C are interior angles of triangle ABC,then show that cos(B+C/2)=sinA/2
Answer» A+B+C = 180°B+C=180°-AB+C/2=90°-A/2Cos(B+C/2)=cos(90°-A/2)Cos(B+C/2)=sin(A/2)Hence proved

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