Mathematics Types 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 N You should see this is… ¾ of a turn = 3 right angles = 3 × 90 = 270° S

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 12 You should see this is… ¼ of a turn = 1 right angle = 90° 6

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.