Nope, curvature is always symmetrical. Use 2 points in close distance.
AS 9.5 MacPro Quadcore 3GHz 16GB OS 10.6.8 Quicktime 7.6.6
AS 11 MacPro 12core 3GHz 32GB OS 10.11 Quicktime 10.7.3
Moho 13.5 iMac Quadcore 2,9GHz 16GB OS 10.15
Moho 14.1 Mac Mini Plus OS 13.5
thank u for your quick answer. i was afraid it would be like u wrote. how else could it could it be in the context of 1 point ? i just thought i heard about it in one tutorial, on installtion-cd, in youtube- i dont know anymore and forgot it after all the time i didnt need it. however. the 2-point-solution is fine too and also crossed my mind.
You could "fake" it with an invisible point too:
But, anyway, I'm with slowtiger here, curvature is always symmetrical. This example just uses that symmetry outside of the shape.