Highly selective Backlog Qs for JEE MainMathematicsParabola
Let the focus S of the parabola y 2 =8 x lies on the focal chord P Q of the same parabola. If P S = 6 , then the square of the slope of the chord P Q is
Options
- A2 5
- B4 5
- C5 4
- D9 4
Correct answer
B. 4 5
Step-by-step solution
We know that, P S , 4 , S Q are in H . P . ⇒ 1 6 , 1 4 , 1 S Q are in A . P . ⇒ 1 S Q = 2 4 - 1 6 = 1 3 ⇒ S Q = 3 ⇒ P Q = 6 + 3 = 9 = 4 c o s e c 2 θ (where, tan θ is the slope of P Q ) ⇒ 1 + cot 2 θ = 9 4 ⇒ cot 2 θ = 5 4 ⇒ tan 2 θ = 4 5