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If length of focal chord P Q is l , and ...

If length of focal chord `P Q` is `l ,` and `p` is the perpendicular distance of `P Q` from the vertex of the parabola, then prove that `lprop1/(p^2)dot`

Text Solution

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From the figure, `PQ=4a" cosec"^(2)theta=l` (given)
Also, in triangle OMS, `sintheta=(p)/(a)`
`:." "l=4a(a^(2))/(p^(2))prop(1)/(p^(2))`
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