Chapter 11 - Surface Area and Volume - 11-1 Space Figures and Cross Sections - Practice and Problem-Solving Exercises - Page 693: 35

The Euler's formula is valid.

Here, we have: $Faces(F)=4$; $Vertices(V)=6$ and $Edges(E)=9$ We will write Euler's formula for two dimensional figures. $F+V=E+1$ or, $4+6=9+1$ or, $10=10$ We can find that both sides are the same which verifies that Euler's formula is valid.