Lindgren's Dissection of a Quadrilateral to a Triangle

a

α

b

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quadrilateral

triangle

move

This Demonstration shows Lindgren's dissection of a quadrilateral to a triangle. The dissection starts with "quadrilateral" selected and the "move" slider to the right. To see the progress of the dissection, move the slider to the left, select "triangle," and move the slider back to the right.