If PSQ is the focal chord of the parabola y^2=8x such that SP=6 then the length of SQ is 

1)3

2)4

3)24

Asked by dineshchem108 | 21st Oct, 2018, 07:54: PM

Expert Answer:

The coordinates of a focal chord of a parabola are P(at2 , 2at) and Q begin mathsize 16px style open parentheses straight a over straight t squared comma space fraction numerator negative 2 straight a over denominator straight t end fraction close parentheses end style
y2 = 8x
comparing with y2 = 4ax we get a = 2
Hence, coordinates of a focus is (2, 0)
SP = 6
SP2 = 36
(2 - 2t2)2 + (4t)2 = 36
Solving it we get
t4 + 2t2 - 8 = 0
t2 = 2
Find SQ we get SQ = 3

Answered by Sneha shidid | 22nd Oct, 2018, 05:39: PM