Find Missing Angles in Special Triangles

In this activity, we are going to be looking at angles in special triangles!

We know that:-   

We can use it to find missing angles in triangles!

Answer

We know that the sum of the three angles is 180^o

We can say that R = 180 - (25 + 96)

R = 180 - 121

R = 59^o

There are two special triangles for us to consider.

1) The Equilateral Triangle

All the sides are the same length.

All the angles are the same.

2) Isosceles Triangle

Two of the sides are the same length. 

Two of the angles are the same

These facts help us to find missing angles in triangles.

Let's have a look at a question.

Example

Calculate the size of angle A in the equilateral triangle below.

Answer

As the triangle is equilateral, we know that all the angles are the same.

We also know that angles in a triangle add up to 180^o

Therefore, angle A = 180 ÷ 3 = 60^o     

Let's try some mixed questions now!