what is the formula for finding the number of angels that can be named by a given number of rays with the same endpoint?

Hi Shon.

Each angle is formed by combining two rays. If you have n rays to choose from, then the number
of possible angles _{n}C_{2}, which equals n! / [ 2 (n-2)! ]. Look up combinations using our
quick search or topics list for more explanation.

Cheers,
Stephen La Rocque.

Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.