# On 2D Inverse Problems/Triangulations of surfaces

From Wikibooks, open books for an open world

Let *G* be a graph embedded to a surface such that all faces of *G* are triangular. Such an embedding is called **triangulation**.

**Exercise (***).** Generalize the examples to prove that the spectra of *G** and *M(G)* are equal, except possibly the eigenvalue {6}.