# isRigid -- checks if a graph is rigid

## Synopsis

• Usage:
r = isRigid G
• Inputs:
• G, an instance of the type Graph,
• Outputs:
• r, ,

## Description

A drawing of a graph is rigid in the plane if any continuous motion of the vertices that preserve edge lengths must preserve the distance between every pair of vertices. A graph is generically rigid if any drawing of the graph with vertices in general position is rigid. This method uses Laman's Theorem to determine if a graph is rigid or not.

 i1 : G = cycleGraph 4; i2 : isRigid G o2 = false i3 : G' = addEdges' (G, {{1,1},{3,1}}) o3 = Graph{0 => {1, 3} } 1 => {0, 1, 2, 3} 2 => {1, 3} 3 => {0, 1, 2} o3 : Graph i4 : isRigid G' o4 = true

## Ways to use isRigid :

• "isRigid(Graph)"

## For the programmer

The object isRigid is .