If tan θ=ab,prove that a sin θ−b cos θa sin θ+b cos θ=a2−b2a2+b2
Tan θ = ab
sinθcosθ = ab------(1)
LHS = asinθ−bcosθasinθ+bcosθ
= asinθcosθ−bcosθcosθasinθcosθ+bcosθcosθ
dividing each term with cosθ
=asinθcosθ−b1asinθcosθ+b1
=a∗ab−b1a∗ab+b1
[from (1)]
= a2−b2a2+b2
=RHS