Original sentence: All points (considered as vectors from the origin) with the same cosine of their angle as measured from the normal vector, and scaled by the distance to the point, are on the same plane.If they cancel each other out, the cosines are the same.is , the (inverted) dot product of the normal vector and the known point on the plane;  is the dot product of the normal and the point being tested
Edited sentence: which is the familiar equation for a plane