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71
The sum of all angles in a quadrilateral is 360°
Polygons: A closed 2-Dimensional shape formed when straight line segments meet at their
endpoints. The line segments are called sides, each endpoint is called a vertex. The
formulas for each type of question appearing in IGCSE examinations relating to Polygons
are shown below.
The exterior angles of a polygon add up to 360° (a°+b°+c°+d°+e°=360°)
The sum of the interior angles of a polygon is denoted by the formula ‘(n–2)x180’ where
n= number of sides of the polygon. In a regular polygon all sides are equal.
Circle Theorems: The properties that illustrate the relationship between angles and the
shapes residing inside a circle. Key properties that will be tested on your IGCSE
examinations are listed below.
Cyclic quadrilateral: The opposite angles within a quadrilateral which lies on the
circumference of a circle always add up to 180°