12.02.21

Well done this week. 

Now we can start to look at angles within shapes.

We are going to begin by looking at triangles.

The angles within a triangle add up to exactly 180º.

Look at the equilateral triangle below. You should notice that all 3 angles are 60°.

60° + 60° + 60° = 180°

Now lets have a look at working out missing angles inside a triangle.

To do this we need to complete 2 steps.

1. Add the angles we do know
2. Subtract the answer from 180

Lets have a look at a few examples.

Step 1

Add the angles we know

70° + 50° = 120°

Step 2

Subtract the answer from 180

180° - 120° = 60°

Step 1

Add the angles we know

68° + 47° = 115°

Step 2

Subtract the answer from 180

180° - 115 = 65°

Now lets have a look at an Isosceles Triangle

Isosceles triangles have 2 angles the same and 1 different.

To work out the angle is an isosceles triangle we follow 2 different steps.

1. Subtract known angle from 180
2. Divide answer by 2

Lets have a look at a few examples.

Step 1

Subtract known angle from 180

180° - 116° = 64°

Step 2

Divide answer by 2

64° ÷ 2 = 32°

Step 1

Subtract known angle from 180

180° - 56° = 124°

Step 2

Divide answer by 2

124° ÷ 2 = 62°

Go onto Purple Mash complete the 2Do named 'Angles in triangles'. Use your home learning books to help you.