This option creates a plane tangent to a curved face. On the Datum Plane dialog, click
Type > Tangent and select a curved face. A plane tangent to the selected face appears.
This method creates a datum plane, which will be normal (perpendicular) to a line, curve,
or edge. On the Datum Plane dialog, click Type > On Curve and select an edge, line,
curve, arc, or circle. Drag the pointer and click on a point to define the location of the plane
(or) type-in a value in the Arc Length box and press Enter.