Dear jacks,

Let,

Then write the gradient of the line. Let it be .

Since and are perpendicular you could find the gradient of the line by,

Then you could fine the equation of the line. Hint: You know the gradient and a point on the line. Let the equation be ----(1)

The equation of the circle could be written as, -----------(2)

Using equations (1) and (2) you can find the point P.