1) Create a line perpendicular to the dotted line through point B.[br]2) Create a circle with a radius equal to AB centered at point B.[br]3) Mark the intersection of the line you made and the circle you made.[br]4) Create a circle with radius equal to AB centered at the point you just marked.[br]5) Create a circle with radius equal to AB centered at point A.[br]6) Mark the intersection of those two circles.[br]7) Use the Polygon tool[icon]/images/ggb/toolbar/mode_polygon.png[/icon] to mark the four vertices of the square: A, B, the point you marked in step 3, and the point you marked in step 6.[br]8) Use the Distance tool[icon]/images/ggb/toolbar/mode_distance.png[/icon] and the Angle Measure tool[icon]/images/ggb/toolbar/mode_angle.png[/icon] to verify that it is a square.