Conic Sections Question 150

Question: At what point on the parabola $ y^{2}=4x $ , the normal makes equal angles with the co-ordinate axes

[RPET 1994]

Options:

A) (4, 4)

B) (9, 6)

C) (4, -4)

D) (1, -2)

Show Answer

Answer:

Correct Answer: D

Solution:

The equation of a normal to $ y^{2}=4x $ at $ (m^{2},-2m) $ is $ y=mx-2m-m^{3}. $ If the normal makes equal angles with the coordinates axes, then $ m=\tan \frac{\pi }{4}=1. $ Thus, the required point is (1, - 2).