[color=#000000]What not-too-often-seen geometry theorem is dynamically being illustrated below?[br](Feel free to move the vertices of the quadrilateral anywhere you'd like!) [br][/color]
[color=#000000][b]Van Aubel's Theorem:[/b][br][br]For any quadrilateral, if squares are built off its four sides, [/color][color=#1e84cc][b]the two segments[/b][/color][color=#000000] that connect [/color][color=#ff00ff][b]centers[/b][/color][color=#000000] of squares on opposite sides (of this quadrilateral) are [/color][color=#1e84cc][b]both congruent[/b][/color][color=#000000] and [/color][b]perpendicular.[/b]