BITSAT 2015 Paper

Put x = sin q and y = sin ϕ
⇒ cos θ + cos ϕ = a (sin t - sin ϕ)
⇒ 2 cos

θ+ϕ

2

cos

θ−ϕ

c

= 2a cos

θ+ϕ

2

sin

θ−ϕ

2

⇒ cot

θ−ϕ

2

=a ⇒ θ - ϕ = 2 cot−1 a
⇒ sin−1−sin−1y = 2 cot−1 a
Differentiate

1

√1−x2

−

1

√1−y2

dy

dx

= 0
so the degree is one