Finding angle between Circle and an intersecting Line

How to find the angle between the tangent at the point of intersection and the intersecting line. Is there any definite formula ?

[Image Analyst]

We know where the tangent line goes - it just barely touches the circle at one point. But where is your "intersecting line" going? What special points does it pass through? The tangent point? The circle center? Somewhere else? Please supply a diagram that shows both of these lines and the circle. And read this first.