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Question Number 197346 by Amidip last updated on 14/Sep/23

Answered by som(math1967) last updated on 14/Sep/23

 ((a+b)/(a−b))=((tan(θ+φ))/(tan(θ−φ)))   ((a+b)/(a−b))=((sin(θ+φ)cos(θ−φ))/(sin(θ−φ)cos(θ+φ)))  ((2a)/(2b))=((sin2θ)/(sin2φ))  [using componendo&dividendo]  asin2φ=bsin2θ  a^2 sin^2 2φ=b^2 sin^2 2θ  a^2 −b^2 =a^2 cos^2 2φ−b^2 cos^2 2θ    now given  acos2φ+bcos2θ=c  (acos2φ−c)^2 =b^2 cos^2 2θ  a^2 cos^2 2φ−2accos 2φ+c^2 =b^2 cos^2 2θ  a^2 cos^2 2φ−b^2 cos^2 2θ  +c^2 =2accos2φ  a^2 −b^2 +c^2 =2accos2φ  [∵a^2 cos^2 2φ−b^2 cos^2 2θ  =a^2 −b^2 ]

a+bab=tan(θ+ϕ)tan(θϕ)a+bab=sin(θ+ϕ)cos(θϕ)sin(θϕ)cos(θ+ϕ)2a2b=sin2θsin2ϕ[usingcomponendo&dividendo]asin2ϕ=bsin2θa2sin22ϕ=b2sin22θa2b2=a2cos22ϕb2cos22θnowgivenacos2ϕ+bcos2θ=c(acos2ϕc)2=b2cos22θa2cos22ϕ2accos2ϕ+c2=b2cos22θa2cos22ϕb2cos22θ+c2=2accos2ϕa2b2+c2=2accos2ϕ[a2cos22ϕb2cos22θ=a2b2]

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