Q11 of 12 Page 595

If A + B + C = π, prove that



Using formula ,






Using ,





Using , since A + B + C = π



And, cos(π – A ) = -cosA




Using , cos2A = 1 – 2sin2A




since A + B + C = π


and Using ,





Using , since A + B + C = π




= 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


 10

If A + B + C = π, prove that

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


 12

If A + B + C = π, prove that

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