The distance between point P and (2, 0) is
So when x = 3 the distance is changing at a rate of
The angle of the line segment formed by this distance is characterized by the slope between the two points:
(I know this isn't standard form, but I'm just going to leave it like this for now.)
Now, geometrically speaking
where is the angle of inclination.
(I'm tired. I'll let you plug in x = 3.)