NTA Abhyas JEE Main2020MathematicsParabolaPractice
O A is the chord of the parabola y 2 = 4 x (where O is the origin). A B is a chord of y 2 = 4 x and perpendicular to O A which cuts the axis of the parabola at C . If the foot of A on the axis of the parabola is D , then the length C D is equal to
Options
- A2 units
- B3 units
- C4 units
- D6 units
Correct answer
C. 4 units
Step-by-step solution
Let, A = t 2 , 2 t The slope of O A is equal to 2 t ⇒ The slope of A B is equal to - t 2 ⇒ The equation of A B is y - 2 t x - t 2 = - t 2 ⇒ C = 4 + t 2 , 0 & D = t 2 , 0 ⇒ C D = t 2 + 4 - t 2 = 4 units