Question
Question: If the normal to the hyperbola xy = c<sup>2</sup> at the point t<sub>1</sub> meets the curve again a...
If the normal to the hyperbola xy = c2 at the point t1 meets the curve again at the point t2 then t1t2 equals.
A
-1
B
−t1−2
C
1/t1
D
1
Answer
-1
Explanation
Solution
Normal at P (ct1, c/t1) is ct13−yt1−ct14+c=0.
If it passes through Q (ct2, c/t2), then
ct2t13−t2ct1−ct14+c=0.
On simplification, we get t1t2 = -1.