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The sum of the reciprocals of focal distances of a focal chord $P Q$ of $y^{2}=4 a x$ is
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Verified Answer
The correct answer is:
$\frac{1}{a}$
Equation of parabola $y^{2}=4 a x$
Total length of focal chord $=4 a$
and half length of focal chord $=2 a$
Now, sum of the reciprocals of focal distances
$$
=\frac{1}{2 a}+\frac{1}{2 a}=\frac{2}{2 a}=\frac{1}{a}
$$
Total length of focal chord $=4 a$
and half length of focal chord $=2 a$
Now, sum of the reciprocals of focal distances
$$
=\frac{1}{2 a}+\frac{1}{2 a}=\frac{2}{2 a}=\frac{1}{a}
$$
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