In what direction a line be drawn through the point (1, 2) so that its points of intersection with the line is at a distance from the given point

The correct answer is:

Let the required line through the point (1, 2) be inclined at an to the axis of x. Then its equation is

where r is the distance of any point (x, y) on the line from the point (1, 2). The coordinates of any point on the line given in Eq. (1) are If this point is at a distance


However, this point lies on the line x y + = 4. So,