Labelling the Outer Points of a Pentagram

[stockgobliin]

Hi,

I'm trying to program an outer point labelling system for pentagrams and I'm having trouble with the logic.

I have 5 pairs of outer x & y coordinates
I have 5 pairs of inner x & y coordinates

I have decided that point "A" is the outer x & y coordinate pair that has an x value closest to the x value of the center of the inner pentagon. That's easy. The center just being the average of the 5 inner pairs.

I would like the outer points to be labelled clockwise from A, B, C, D & E.

What logic can I use to determine which point is which?

Any help is appreciated.

Thanks

 

[stapel]

What do you mean by an "outer point labeling system"? What is the definition of an "inner" and an "outer" point? Since you have the points, why are you needing a "logic" for labeling? Can't you just graph the points and label from whichever starting point you like?

 

[mmm4444bot]

I'm thinking that the outer points are the tips of the star and the inner points are the intersections of the star's sides.

It also seems (to me) that pre-knowledge of how the pentagram is oriented with respect to the coordinate axes would be required, in order to develop a system, but with additional brainstorming perhaps not.

(For example, I was thinking that the x-coordinate of point C would need to be between the x-coordinates of points A and B -- if the thing were oriented such that a line drawn through C and D is parallel to the x-axis. If so, maybe a system could be developed that uses comparisons of x-coordinates.)

Take a look at equations (5) through (8) -- along with the two related diagrams above them -- at this Wolfram page. Maybe that info will give you some other ideas.

Cheers :cool: