Interior angle sums, interior and exterior angles of regular polygons, and working back to the number of sides.
What you will learn
- Find the interior angle sum of any polygon
- Find interior and exterior angles of a regular polygon
- Find the number of sides from an angle
Names of polygons
A polygon is a flat shape with straight sides.
A regular polygon has all its sides equal and all its angles equal.
Names by number of sides: triangle 3, quadrilateral 4, pentagon 5, hexagon 6, heptagon 7, octagon 8, nonagon 9, decagon 10, dodecagon 12.
A regular triangle is an equilateral triangle, and a regular quadrilateral is a square.
The rest of this lesson and its 7 practice questions are locked.
In this lesson
- Names of polygons
- Two facts for every polygon
- Shapes that tessellate
- Try it: Check with the calculator
7 practice questions, marked as you go; about 25 minutes in all.
Key terms
Polygon, Regular, Equilateral triangle, Square, Tessellate
In this unit: Angles, polygons and parallel lines
Angle facts on lines, at points and in triangles, angles with parallel lines, quadrilaterals, interior and exterior angles of polygons, and chains of reasoning.