Trigonometrical Ratios and Identities 1 Question 28

28. Prove that sin2α+sin2βsin2γ=2sinαsinβsinγ, where α+β+γ=π.

(1978,4M)

Integer Answer Type Question

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Solution:

  1. LHS =sin2α+sin2βsin2γ

=sin2α+(sin2βsin2γ)=sin2α+sin(β+γ)sin(βγ)=sin2α+sin(πα)sin(βγ)[α+β+γ=π]=sin2α+sinαsin(βγ)=sinα[sinα+sin(βγ)]=sinα[sin(π(β+γ))+sin(βγ)]=sinα[sin(β+γ)+sin(βγ)]=sinα[2sinβcosγ]=2sinαsinβcosγ= RHS 



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