JEE Advanced2013MathematicsParabolaActual
Paragraph: Let P Q be a focal chord of the parabola y²=4 a x . The tangents to the parabola at P and Q meet at a point lying on the line y=2 x+a, a>0 . Question: If chord P Q subtends an angle at the vertex of y²=4 a x , then =
Options
- A2 3 7
- B- 2 3 7
- C2 3 5
- D- 2 3 5
Correct answer
D. - 2 3 5
Step-by-step solution
t - 1 t = - 1 ⇒     t + 1 t = 5 tan  θ = 2 t + 2 t 1 - 4 = 2  1 t + t - 3 = 2 5 - 3