This is an important question from the
Book- ML Aggarwal
Chapter- Trigonometric Identities
If x – a sec θ + b tan θ and y = a tan θ + b sec θ, prove that x2 – y2 = a2 – b2.
Trigonometric Identities, class 10th, chapter 18th, question no34 , ICSE board, ML aggarwal..