MATHEMATICSTypes of Angles

Aims of the Lesson

• To learn key words and facts linked with turning and position.

• To recognise and name the different types and sizes of angles.

Lead-In

• Before you continue to work through this powerpoint, please make sure you have worked through the following MyMaths lesson first:

Shape > Angles > Position and Turning

• It can be found at this link: • http://app.mymaths.co.uk/253-resource/position-and-turning

Angle

• Length is a measure of distance.• Units of length vary… millimetres, centimetres, metres etc.

• Angle is a measure of turning.• Its units can also vary but until you reach A’ level mathematics, you will only use the units of ‘degrees’.

Turning

• You will need to learn that…

¼ turn = right angle = 90°

½ turn = semi-circle = straight line = 180°

¾ turn = 3 right angles = 270°

1 full turn = circle = 360°

Turning Situations

• The turning descriptors you come across may relate to…

• Directions (North, South, East, West)

• Time (i.e. the movement of hands on a clock face)

• Shapes and their properties (but more about these later)

Turning Example using Direction

• If I am facing North and I turn in a clockwise direction to face West, through what angle have I turned?

W E

S

You should see this is…

¾ of a turn

= 3 right angles

= 3 × 90

= 270°

N

Turning Example using Time

•The minute hand of a clock moves from 10:45 to 11:00, through what angle does it travel?

9 3

6

You should see this is…

¼ of a turn

= 1 right angle

= 90°

12

Right Angles• You need to recognise right angles.

• These measure 90°

• Imagine a horizontal and vertical line meeting, they make an angle of 90°

• However, the angles you come across may not have horizontal or vertical lines but may still meet at right angles!

• If lines meet at right angles then they are ‘perpendicular’

Right Angles

• All of these diagrams show right angles• If the angle is not a right angle or the size is unknown, it would be shown with a curve but as we know these ARE right angles a ‘square’ corner is used.

Other Types of Angles

• ACUTE angles are less than 90°

• RIGHT angles are exactly 90°

• OBTUSE angles are between 90° and 180° (not inc.)

• STRAIGHT angles are exactly 180°

• REFLEX angles are between 180° and 360° (not inc.)

What next?

• Print out the notes called Angle1-Types.docx. Read through them and make sure you answer any questions.

• Save and complete the worksheet called: Angles.xlsx

• Now move on to the Angle2 powerpoint.