How to find a circle that goes though two points?

Question

In Google Sketch-up you can draw two lines at 90 degrees to each other and using the arc tool you can find the tangent at vertex.

http://img151.imageshack.us/img151/4074/tangentatvertexiv3.png

I need to know how to find the radius of this circle.

http://img529.imageshack.us/img529/8226/tangentatvertexpw0.png

Obviously in this case the radius is equal to the height.

But in a case where the two lines are of different lengths I haven't got a clue how.

I need to know how to do this for a program I am making in which you can enter dimensions of space you have and it can calculate and form plans for a skateboard ramp which you can then use in real life to make a ramp. Obviously in Sketch-up you can just use the tape measure tool to find this length.

Thanks in advance for your help

~DRew

Answer 1

if it is a circle and the tangent line are at 90 degrees then it is not possible to have different length