4.5  SUMMARY:

1. A triangle has six elements 3 sides and 3 angles.

2. To construct a triangle, 3 elements out of six elements are required under a certain combination.

3. A quadrilateral has 8 elements 4 sides and 4 angles.

4. In addition to these elements a quadrilateral has 2 diagonals which play an important role in determining the size and shape of a quadrilateral.

5. Thus a quadrilateral has 10 elements (4 sides, 4 angles and 2 diagonals) or measurements.