Let a line perpendicular to the line 2x - y = 10 touch the parabola y2 = 4(x - 9) at the point P. The distance of the point P from the centre of the circle x2 + y2 - 14x - 8y + 56 = 0 is .
Answer
10
Solution
Slope of 2x - y = 10 is 2 slope of the tangent m = - 12
y2 = 4(x - 9): a = 1, vertex (9, 0) point of contact (9 + am2, 2am )
P(9 + 4, -4) = (13, -4)
Centre of the circle: C(7, 4)
CP = (13 - 7)2 + (-4 - 4)2 = 36 + 64 = 10
Answer: 10