2D polygons

Elementary geometry in 2 dimensions

Triangles

Area of a triangle

Circumference of a triangle

Sum of angles of a triangle

Angles in a triangle add to \(\pi\).

Quadrilaterals

Oblongs

Area of an oblong

Circumference of an oblong

Squares

Area of a square

\(A=l^2\)

Circumference of a square

\(C=4l\)

Angles in a square

Angles in a square sum to \(2\pi\).

Pentagon

Other

Border

Interior

Open

Closed

Self-intersecting polygon