Theory:

We can define a quadrilateral in two ways:
  • A quadrilateral is a closed-form that is obtained by joining four points which are non-collinear to any three points.
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  • A quadrilateral is a shape which is closed with four vertices and four sides.
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We can say that there are four sides, four angles, and four vertices are in a quadrilateral.
 
Think of the following quadrilateral, for example:
 
A quadrilateral \(ABCD\) will have two diagonals: \(AD\) and \(BC\).
 
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Quadrilateral specific properties are:
  • They have \(4\) sides.
  • They have \(4\) vertices.
  • They have \(2\) diagonals.
  • The sum of all interior angles is \(360°\).
We will study in detail about the other properties of various quadrilaterals in the next theory.