This Geometer's Sketchpad lab has students first investigate the theorem that any point on the perpendicular bisector is equidistant from the endpoints. Then it follows with a lab to construct the circumcenter and circumscribed circle. I usually use this after I have discussed the basics of a perpendicular bisector and how to construct with a compass and straightedge. The last 3 pages are questions pertaining to circumcenter with some review questions with incenter. The last 2 questions have students construct the circumcenter on graph paper practicing midpoint, slope and distance formulas.