Lindgren's Two-Triangles-to-One Dissection
Lindgren's Two-Triangles-to-One Dissection
Lindgren used a quadrilateral slide to transform one triangle (as a trapezoid with a top edge of length 0) to a trapezoid with the same angles.A quadrilateral slide (or Q-slide) transforms one quadrilateral to another with the same angles. The notion was introduced by Lindgren (1956).