Q10 of 12 Page 595

If A + B + C = π, prove that

sin2 A – sin2 B + sin2 C = 2sin A cos B sin C


= sin2 A – sin2 B + sin2 C


Using formula ,






Using ,





since A + B + C = π



And sin(π – A) = sinA




Using , cos2A = 1 – 2sin2A











= 2sinAcosBsinC


= R.H.S


More from this chapter

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8

If A + B + C = π, prove that


 9

If A + B + C = π, prove that

cos2 A + cos2 B + cos2 C = 1 – 2cos A cos B cos C


 11

If A + B + C = π, prove that


 12

If A + B + C = π, prove that

tan 2A + tan 2B + tan 2C = tan 2A tan 2B tan 2C