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How to Use Diagonals to Identify Quadrilaterals

Any four-sided shape is a quadrilateral as long as each side is a straight line and the shape is two-dimensional (that is, it can be drawn on a page). However, many special quadrilaterals exist, including squares, rectangles, parallelograms, rhombuses, trapezoids and kites. The diagonals of a quadrilateral are lines between the points that are not already connected by lines. These can distinguish some named quadrilaterals from each other.

Instructions

- 1
  Check if any of the lines are parallel. If no pairs of lines are parallel, then you do not have a special quadrilateral. If some pair is parallel, continue to the following steps.
- 2
  Find the angle between the two diagonals, using a protractor. If the angle between the lines is 90 degrees, the quadrilateral is either a kite, a square, a rectangle or a rhombus.
- 3
  Measure the two diagonals. If they are the same length, the quadrilateral is either a square, a rectangle or a rhombus.

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