# Names of triangles: Properties of scalene, isosceles and equilateral triangles.

There are basically three types of triangles that you need to remember for your maths exams, these are scalene, isosceles and equilateral triangles.

The **scalene triangle**
is probably the least interesting of the three triangles. A scalene triangle
has three different side lengths and three different angles.

An **isosceles triangle**
is one which has two equal side lengths and two equal angles. It also has one
line of reflectional symmetry. A typical maths question on isosceles triangles
will be to work out the missing angles inside the isosceles triangle if already
given one of the angles.

Example

Work out the missing angles in this isosceles triangle.

First of all take the angle you are given from 180⁰ as the angles in a triangle add up to 180⁰.

180 – 16 = 164⁰.

Once this is done, all you need to do now is half this answer as the two angles at the bottom of the triangle are the same size (because the triangle is isosceles).

Therefore, if you halve 164 you get answer of 82⁰.

So the two angles at the bottom of the triangle are 82⁰.

An **equilateral triangle**
has three equal side lengths and three equal angles. Since all the angles in a
triangle add up to 180⁰ and an equilateral triangle has 3 equal sides, then the
interior angles can be found by dividing 180 by 3. This gives the interior
angle of an equilateral triangle of 60⁰.
Also an equilateral triangle has 3 lines of reflectional symmetry and
order 3 rotational symmetry.