2D shape and pattern
Types of triangles
Triangles are named by how many of their sides (and angles) are equal.
The three types
ā¢ Equilateral ā all 3 sides equal and all 3 angles equal. ā¢ Isosceles ā exactly 2 sides equal and 2 angles equal. ā¢ Scalene ā no equal sides and no equal angles.
Worked examples
Equilateral
- All three sides are the same length.
Answer: It is an equilateral triangle.
Isosceles
- A triangle has sides 5 cm, 5 cm and 8 cm.
- Two sides are equal.
Answer: It is an isosceles triangle.
Scalene
- A triangle has sides 3 cm, 4 cm and 5 cm.
- All three sides are different.
Answer: It is a scalene triangle.
Where you see this in real life
- Triangles make bridges and roofs strong.
- Road signs are often equilateral triangles.
- Spotting different triangles in buildings and patterns.
Key words
- Equilateral triangle
- A triangle with three equal sides and three equal angles.
- Isosceles triangle
- A triangle with exactly two equal sides and two equal angles.
- Scalene triangle
- A triangle with no equal sides and no equal angles.