GEOMETRY • REGULAR AND IRREGULAR POLYGONS 213
Regular and irregular
polygons
A polygon is a 2D shape made of straight sides. Regular polygons have sides
that are all the same length and angles of equal size. Irregular polygons have
sides of different lengths and different-sized angles.
TRY IT OUT
Odd one out
Only one of these five-sided
polygons is a regular polygon, with
sides of the same length and equal-
sized angles. Can you spot it?
Regular triangle Irregular triangle
Irregular quadrilateral
Irregular hexagon
Regular quadrilateral
Answer on page 320
All six sides are the
same length, and the
angles are equal
All three sides are different
lengths, and the angles are
different sizes
The sides can be
different lengths
Regular hexagon
Triangle
A regular triangle has a special
name – an equilateral triangle.
Different irregular triangles also
have special names. Find out
more on page 215.
Quadrilateral
Quadrilaterals are four-
sided shapes. A regular
quadrilateral is called a square.
Hexagon
A six-sided polygon
is called a hexagon.
212_213_2D_shape_Regular_irregular_polygons.indd 213 29/02/2016 18:04