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The length of the latus rectum of the pa...

The length of the latus rectum of the parabola `x^2 −4x−8y+12=0`is

A

4

B

6

C

8

D

10

Text Solution

Verified by Experts

The correct Answer is:
B
Let tangent at `P(at^(2),2at)` make an angle `theta` with x-axis.
Then `tan theta = (1)/(t)`
Projection of BC on tangent
`= BC sin theta = (4a)/(sqrt(1+t^(2))) ge 2a sqrt(2) (as -1 le t le 1)`
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