If a sec θ = x and b tan θ = y, then find correct relation.

Putting a = b = 1

option b) becomes ; b²x² - a²y² = a²b²

⇒ b² (a²) sec² θ - a² (b tan² θ) = a²b²

⇒ (a²b²) (sec² θ - tan² θ) = a²b²

⇒ sec² θ - tan² θ = 1

which is true

b²x² - a²y² = a²b²