If sin2A=λ sin2B,provethat:tan(A+B)tan(A−B)=λ+1λ−1
We have
sin2A=λ sin2B⇒λ=sin2Asin2B
Now,
λ+1λ−1=sin2Asin2B+1sin2Asin2B−1=sin2A+sin2Bsin2Bsin2A−sin2Bsin2B=sin2A+sin2Bsin2A−sin2B=2sin(2A+2B2)cos(2A−2B2)2sin(2A−2B2)cos(2A+2B2)=sin(A+B)cos(A−B)sin(A−B)cos(A+B)∴ λ+1λ−1=tan(A+B)tan(A−B)⇒tan(A+B)tan(A−B)=λ+1λ−1