Solve Angle Problems Using Given Rules

In this activity, we will calculate missing angles using different angle rules.

 

Let's recap the rules first!

 

Recap - Make a note of these!

 

Angles at a point = 360^o

Angles on a straight line = 180^o

Angles in a triangle = 180^o

Angles on parallel lines - Z shape-  angles are equal -  alternate angles

Angles on parallel lines - F shape-  angles are equal -  corresponding angles

Angles on parallel lines - C shape-  angles add up to 180^o -  co-interior angles

Vertically opposite angles - X shape - opposite angles are equal.

 

 

Let's look at a typical question!

 

Example

Calculate the missing angle A, giving reasons.

 

 

Answer

Step 1 - We can see a vertically opposite angle (X shape) with 52^o

 

 

Step 2 - We know that angles in a triangle add up to 180^o

We have 55^o and 52^o so we can subtract to find angle A.

 

Angle A = 180 - (52 + 55)

A = 180 - 107

A = 73^o

 

Let's try some more questions!