Episode 01 – Finding Pick's formula

Pick's formula. Definition (Notations). For any polygon P in a lattice, we note BP the number of points on its border and IP the number of points strictly inside the ...
234KB taille 5 téléchargements 51 vues
Episode 01 – Finding Pick’s formula European section – Season 3

Episode 01 – Finding Pick’s formula

What is a lattice ? Definition (Lattice) A lattice is a square grid, a discrete surface with a regular gap between any two points. A simple example is the set of the points with whole coordinates on a coordinate graph. Example bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

Episode 01 – Finding Pick’s formula

Lattices polygons

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

Episode 01 – Finding Pick’s formula

Pick’s formula Definition (Notations) For any polygon P in a lattice, we note BP the number of points on its border and IP the number of points strictly inside the polygon. The area of the polygon will be noted AP .

Episode 01 – Finding Pick’s formula

Pick’s formula Definition (Notations) For any polygon P in a lattice, we note BP the number of points on its border and IP the number of points strictly inside the polygon. The area of the polygon will be noted AP . Example

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

BP IP

Episode 01 – Finding Pick’s formula

= =

Pick’s formula Definition (Notations) For any polygon P in a lattice, we note BP the number of points on its border and IP the number of points strictly inside the polygon. The area of the polygon will be noted AP . Example

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

BP IP

Episode 01 – Finding Pick’s formula

= =

5

Pick’s formula Definition (Notations) For any polygon P in a lattice, we note BP the number of points on its border and IP the number of points strictly inside the polygon. The area of the polygon will be noted AP . Example

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

BP IP

Episode 01 – Finding Pick’s formula

= =

5 13

Find a formula involving the numbers BP and IP to compute the area of any lattice polygon.

Episode 01 – Finding Pick’s formula

Theorem For any convex polygon P in a square two-dimensional lattice, AP =

1 BP + IP − 1. 2

Episode 01 – Finding Pick’s formula

Theorem For any convex polygon P in a square two-dimensional lattice, AP =

1 BP + IP − 1. 2

Example

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

BP

=

5

IP

=

13

AP

=

Episode 01 – Finding Pick’s formula

Theorem For any convex polygon P in a square two-dimensional lattice, AP =

1 BP + IP − 1. 2

Example

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

BP

=

5

IP

=

AP

=

13 1 BP + IP − 1 2

Episode 01 – Finding Pick’s formula

Theorem For any convex polygon P in a square two-dimensional lattice, AP =

1 BP + IP − 1. 2

Example

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

BP

=

5

IP

=

AP

=

AP

=

13 1 BP + IP − 1 2 5 + 13 − 1 2

Episode 01 – Finding Pick’s formula

Theorem For any convex polygon P in a square two-dimensional lattice, AP =

1 BP + IP − 1. 2

Example

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

bc

BP

=

5

IP

=

AP

=

AP

=

AP

=

13 1 BP + IP − 1 2 5 + 13 − 1 2 29 2

Episode 01 – Finding Pick’s formula