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the locus of the mid point of the line segment joining the focus to a moving point on the parabola y^2 = 4ax is another parabola with directrix ? ( main issue - how to eliminate t to get the equation of locus )

the locus of the mid point of the line segment joining the focus to a moving point on the parabola y^2 = 4ax is another parabola with directrix ? ( main issue - how to eliminate t to get the equation of locus )

Grade:Upto college level

1 Answers

Jitender Singh IIT Delhi
askIITians Faculty 158 Points
8 years ago
Ans:
Focus O of the parabola:
(a, 0)
Moving point P on the parabola:
(at^{2}, 2at)
Let the mid point of OP to be:
(h, k)
h = \frac{at^{2}+a}{2}, k = at
2h = at^{2} + a
t = \frac{k}{a}
k^{2} = 2ah - a^{2}
Replace
h \rightarrow x, k \rightarrow y
y^{2} = 2ax - a^{2}
x = 0
is the directrix.
Thanks & Regards
Jitender Singh
IIT Delhi
askIITians Faculty

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