1. The problem statement, all variables and given/known data Go to the following web site: http://www.astro.utoronto.ca/~cclement/cat/listngc.html This is the portal to a large on-line catalog of variable stars in globular clusters. Each link is a cluster name and will take you to a simple text page that lists near the top the coordinates of the cluster. Below that is an explanation of the data in the table, followed by a list of variable stars in the cluster. Each variable star entry lists the ID, RA and Declination of the star along with other information not relevant to this problem. Choose a few of the clusters until you find one that has at least ten variable stars listed in its catalog page. For these ten (or more) stars, use the spherical sine and cosine laws to calculate i) the angular distance of each star from the cluster center in arcmin and ii) the ‘position angle’ (or PA) of each star relative to the cluster center in deg. The PA is defined so that if a star is located directly north of the cluster center is at =0deg=360 , while a star directly east is at =90 2. Relevant equations 3. The attempt at a solution How do I get the central point of the cluster? And I don't know how to interpret those position coordinates?