To Construct The Greatest Square Within A Given Circle. -(Fig. 55.) Draw the diameter, ab, and place the angle of the square upon the circumference within the circle, moving the square until equal figures upon both Bl. and To. rest upon the diameter at its intersection with the circle. The angle of the square should be marked c upon the circumference; a line drawn through the center of the circle from c to the other side will give d, or the fourth corner of the square. Connect a, c, b, d, with straight lines.