This is a prototype of JavaSketchpad, a World-Wide-Web component of The Geometer's Sketchpad. Copyright ©1990-1998 by Key Curriculum Press, Inc. All rights reserved. Portions of this work were funded by the National Science Foundation (awards DMI 9561674 & 9623018).

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We want to see if the above frame is stable or not. This can be found by looking at the associated bipartite graph which consists of three row vertices corresponding to three rows and five column vertices corresponding to five columns of the above frame, and an edge is conneted between a row vertex and a column vertex if there is a diagonal supporter. A frame is stable if and only if its cooresponding bipartite graph is connected. For the above frame, the bipartite graph is not connected, so it is not stable. Yonggu Kim.

Try to move the left one of two red points.