Hi,

I am now trying to make an ellipse in a quadrangle, ABCD

as is shown in image59.jpg.

It may be a part of perspective view.

I think the center of the ellipse is the center of gravity of quadrangle ABCD.

In numerical calculation in Visio, the center of ellipse is

close to the center of gravity in about 0.01 mm.

But I cannot find how it is proved geometrically.

If it is proved and if it is right, the calculation of the parameters may be simplified.

I think calculation may be done in shapesheet.

Calculation may be faster and more simple than that done with VBA.

Any idea?