1) Find the perpendicular bisectors of TWO of the sides of the triangle.[br]2) Use the Intersect tool[icon]/images/ggb/toolbar/mode_intersect.png[/icon] to mark the point where the two perpendicular bisectors intersect.[br]3) Use the Compass tool[icon]/images/ggb/toolbar/mode_compasses.png[/icon] to create a circle with a radius equal to the distance from that point to any vertex of the triangle, centered on the point you created in step 2.