In details



Quadrangle It is a four-sided polygon.

Quadrangle A B C D

In a quadrangle, two sides or two nonconsecutive angles are called opposites.


In the figure below, we have:

Quadrangle A B C D

Vertices: A, B, C, and D.

Internal angles or angles of
ABCD quad: .


  1. Every quad has two diagonals.

  2. The perimeter of a quadrilateral ABCD is the sum of the measurements on its sides, ie AB + BC + CD + DA.

Concave and Convex

The quads can be convex or concave. A quad is convex when the line joining two consecutive vertices does not find the side formed by the two other vertices.

Convex Quad

Concave Quad

Next: Sum of Inner Angle Measurements