[hcw]

In Plane Geometry, planes have no mass -- they are shapes in space.

The "three points" you refer to don't necessarily define the shape of the plane. You can have planes that are shaped like rectangles, circles, squares, triangles or any shape.

However, any plane can be defined by any three "coplanar" points -- i.e., three points that are lying on the plane you wish to define. Thus, you can have three points -- A, B, and C -- on a large circle-shaped plane. Lines drawn between the three points would describe a triangle -- but those three points would still define to which plane you refer(as would any other three points on the same plane).

For example, you could describe a street as Mr. Brown's street or, his neighbor, Mr. Green's street. That would identify the street, but wouldn't tell you the shape of the street.

Most people think of The Golfing Machine plane as a huge rectangle -- and, it could be. It could also be a large circle, square, etc. Mr. Kelley never described the shape of the plane -- he only said that it had to be larger than the cirucumference of the club being swung (2-F).

i agree...my thinking was that this plane extended forever above, below, to the right and to the left of the golfer....but as you said, you only have to imagine it being larger than your club circumfrence...