If A+B+C=π , prove that sin 2A + sin2B + sin2C =4sinA*sinB*sinC
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Answer:
LHS
=sin2A+sin2B+sin2C
=(sin2A+sin2B)+sin2C
=2sin (A+B)cos (A-B)+2sicCcosC
=2sin (pi-C)cos(A-B)+2sinCcosC
=2sinC [cos (A-B)+cosC]
=2sinC [cos(A-B)+cos{pi-(A+B)}]
=2sinC [cos(A-B)-cos (A+B)]
=2sinC [2sinAsinB]
=4sinAsinBsinC (proved)=RHS
Hope it help you ☝☝
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