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Euler’s Formula
A Naturally Occurring Function
Leonhard Euler was a brilliant Swiss mathematician. He is
often referred to as the “Beethoven of Mathematics.”
Euler discovered an interesting relationship between the number of faces, vertices, and edges for
any polyhedron.
Poly-what?
A polyhedron is a 3 dimensional shape with flat sides.
All prisms and pyramids are examples of polyhedra (plural for
polyhedron).
POLYHEDRA
PRISMS PYRAMIDS
Any polyhedron has faces, vertices, and edges.
EDGE
FACE
VERTEX
A face is a flat side.
This rectangular prism has 6 faces.
This rectangular prism has 6 faces.
FRONT
This rectangular prism has 6 faces.
FRONT
BACK
This rectangular prism has 6 faces.
FRONT
BACKTOP
This rectangular prism has 6 faces.
FRONT
BACKTOP
BOTTOM
This rectangular prism has 6 faces.
FRONT
BACKTOP
BOTTOM
LEFT
This rectangular prism has 6 faces.
FRONT
BACKTOP
BOTTOM
LEFT
RIGHT
BACK
This rectangular prism has 6 faces.
FRONT
TOP
BOTTOM
LEFT
RIGHT
BACK
This rectangular prism has 6 faces.
FRONT
BOTTOM
LEFT
RIGHT
TOP
BACK
This rectangular prism has 6 faces.
FRONT
BOTTOM
LEFT
RIGHT
TOP
BACK
This rectangular prism has 6 faces.
FRONT
BOTTOM
LEFT
RIGHT
TOP
BACK
This rectangular prism has 6 faces.
FRONT
BOTTOM
LEFT
RIGHT
TOP
This square pyramid has 5 faces.
The faces consist of 4 triangles and a square.
The faces consist of 4 triangles and a square.
A triangular pyramid has 4 faces.
A triangular pyramid has 4 faces.
A triangular pyramid has 4 faces.
A triangular pyramid has 4 faces.
A triangular pyramid has 4 faces.
A triangular pyramid has 4 faces.
An edge is a line segment where two faces meet.
A rectangular prism has 12 edges.
A triangular pyramid has 6 edges.
A vertex is a corner. It is a point that connects 2 or
more edges.
A vertex is a fancy word for “corner.”
Every triangle has 3 vertices (corners).Points A, B, and C are vertices.
A B
C
A rectangular prism has 8 vertices.
A rectangular prism has 8 vertices.
A triangular pyramid has 4 vertices.
A triangular pyramid has 4 vertices.
Euler studied the faces, vertices, and edges of different polyhedra.
Like most great mathematicians and scientists, he organized his
data in a chart. Polyhedron # of Faces # of Vertices # of Edges
Cube 6 8 12
Sq. Pyramid 5 5 8
Tri. Prism 5 6 9
Euler looked for a relationship between these numbers.
Polyhedron # of Faces # of Vertices # of Edges
Cube 6 8 12
Sq. Pyramid 5 5 8
Tri. Prism 5 6 9
Can you determine Euler’s formula that relates the # of Faces and # of Vertices to
the # of Edges?
Polyhedron # of Faces # of Vertices # of Edges
Cube 6 8 12
Sq. Pyramid 5 5 8
Tri. Prism 5 6 9
Faces + Vertices –2 = Edges
Polyhedron # of Faces # of Vertices # of Edges
Cube 6 8 12
Sq. Pyramid 5 5 8
Tri. Prism 5 6 9
+ - 2 =
+ - 2 =
+ - 2 =
Use Euler’s Formula to determine the number of edges in
a pentagonal prism.Polyhedron # of Faces # of Vertices # of Edges
Cube 6 8 12
Sq. Pyramid 5 5 8
Tri. Prism 5 6 9
Pent. Prism 7 10
+ - 2 =
+ - 2 =
+ - 2 =
Use Euler’s Formula to determine the number of edges in
a pentagonal prism.Polyhedron # of Faces # of Vertices # of Edges
Cube 6 8 12
Sq. Pyramid 5 5 8
Tri. Prism 5 6 9
Pent. Prism 7 10
+ - 2 =
+ - 2 =
+ - 2 =
+ - 2 =
Use Euler’s Formula to determine the number of edges in
a pentagonal prism.Polyhedron # of Faces # of Vertices # of Edges
Cube 6 8 12
Sq. Pyramid 5 5 8
Tri. Prism 5 6 9
Pent. Prism 7 10 15
+ - 2 =
+ - 2 =
+ - 2 =
+ - 2 =
SUMMARY:Euler’s Formula says that if you
add the number of faces and vertices, then subtract by 2, the result is the number of edges.
Euler’s Formula works for any polyhedron.
THE END!