Distance between point and a plane

[M_Almostafa]

Hallo,

How to profe if the point p (10,10,-20)

Lie on the Plane E(-40/20/-30)

Thanks

[Kent1Cooper]

[Maybe my mathematical education was lacking, but explain in more detail how E(-40/20/-30) defines a plane.  I know how three points can, but not just three numbers.]

If the User Coordinate System is currently set to match the plane in question, then this:

(trans '(10 10 -20) 0 1)

will tell you the coordinates of that point in terms of the current UCS.  If the third number in the resulting list [the Z coordinate] is 0.0, the point lies in the plane.  Whether zero or not, that number's absolute value is the distance between the point and the plane.