How can I find the location of a circle and creat a cylindrical system using three vertex on the circle.

Thanks!

VCENTER, NV(1), NV1, NV2, NV3, RADIUS: Given two vertices on a circle and a radius or three vertices on a circle, this command calculates the centre of the circle and puts vertex NV at that location.

and

VLOCAL, ICSYS, SYSTEMTYPE, NVORIG(0), AXIS1, NV1, AXIS2, NV2,RMAJOR: Defines a local coordinate system using three predefined vertices.

I have got it! Thank you very much!