Conic Sections Question 70

Question: The locus of a foot of perpendicular drawn to the tangent of parabola $ y^{2}=4ax $ from focus, is

[RPET 1989]

Options:

A) $ x=0 $

B) $ y=0 $

C) $ y^{2}=2a(x+a) $

D) $ x^{2}+y^{2}(x+a)=0 $

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Answer:

Correct Answer: A

Solution:

Tangent to parabola is, $ y=mx+\frac{a}{m} $ …..(i) A line perpendicular to tangent and passing from focus $ (a,0) $ is, $ y=-\frac{x}{m}+\frac{a}{m} $ ……(ii) Solving both lines (i) and (ii)

therefore $ x=0 $ .