Geometry: using only compasses and straightedge
Draw a square method 2
Draw a line AB. Mark any point X below AB.
With compasses on X, width (radius) XA, draw a circle.
Draw a line through Y and X crossing the circle at Z
Draw a line through A and Z to F.
Use compasses with radius (width) AB cut AF at D.
AD is the second side of the square.
Centre the compasses at D and B with radius AB, draw arcs crossing at C.
Centre the compasses at D and B with radius AB, draw arcs crossing at C.
Join ABCD and you have a perfect square.