how calculate core an ellipse twin points radius sizes

while operative svg doing internet path-finder formed the possess vml format i came problem interpretation an svg elliptical arc an vml elliptical arc.

in vml an arc given by: twin angles twin points ellipse lengths radiuses,
in svg an arc given by: twin pairs coordinates twin points ellipse sizes ellipse range box

so, doubt is: demonstrate angles twin points ellipse twin pairs coordinates.
an middle doubt be: core an ellipse coordinates camber points the curve.

update: let's have precondition observant an ellipse customarily placed (its radiuses together linear coordinate component axis), so series applied.

update: doubt associated svg:ellipse element, rather "a" elliptical arc management svg:path component ()