Drawing an Arc

I would like to take an existing line defined by (X1, Y1) – (X2, Y2) and select a third coordinate (X3, Y3) anywhere in between curving the line to encompasses all three points.

I’m able to draw an Arc with a center point & radius specifying a start and stop position in radians / degrees, but this makes exact placement quite difficult and almost impossible to animate.

The goal is to alter / animate a given line, bending it back and forth in real time, graphically displaying measured stress & yield levels.