A tangent to a circle is perpendicular to the radius of the circle at the point of tangency. That means that in quadrilateral AOBC, angles A and B are right angles and measure 90 deg.
The sum of the measures of the angles of an n-sided polygon is
The minimum of this graph is the focus of the parabola. I'm not sure with the maximum though but I think it doesn't have a maximum because the y value of the parabola will extend infinitely upward.
