Calculate Angles in Triangles and on Parallel Lines

Look at the following diagram.

We can use our knowledge of angle rules to work out all the missing angles.

Angle aº = 58º because it is alternate to the 58º on parallel lines (Z or S shape)

Angle bº = 48º because it is alternate to the 48º on parallel lines (Z or S shape)

Angle cº = 180º - 48º - 58º = 74º for two reasons.....angles in a triangle add up to 180º and angles on a straight line add up to 180º

Angle dº = 180º - 58º = 122º because angles on a straight line add up to 180º

Let's have a go at some questions now.

You can look back to this page for a reminder of the rules by clicking on the pink button at the side of the activity.