Ah ok, well thats really straightforward, just compute the cross product between your vector and the ‘normal’ vector of the arc (an arc is always on a plane, so I created one using the same inputs as the arc to obtain the ‘normal’, but you can easily do this from points on the arc etc) then project the centre point of the arc onto itself using the result of the cross product.

The vector can be defined however you like.

EDIT: Also, arcs, ellipses, polygons and circles should have a GetPlane() method/node cc @Michael_Kirschner2 @Aparajit_Pratap