Page 98 - Knowledge Organiser Yr9 24-25

Knowledge Base: Mathematics Topic 30: Bearings and Scale Year 9 | Spring Term, 1st Half
By the end of this topic you should be able to:
• Interpret scale drawings
• Calculate angles in parallel lines
• Measure and state bearings
• Understand where a bearing is from including back bearings
• Calculate bearings using angle rules
• Use ratios to interpret scale drawings
Language
Meaning
Example
Construct
To draw a shape accurately using a ruler, protractor and pair of compasses.
Drawing an SAS triangle is a construction.
Bisect
To divide into two equally.
Midpoint of a straight line bisects it.
Perpendicular bisector
A line that cuts a second line at 90°.
See example below.
Locus (plural loci)
The locus of an object is its path.
A circle is the locus of points equidistant from a fixed point.
Bearing
An angle, measured clockwise from north and quoted using three figures, used to describe a direction.
East has a bearing 090° West has a bearing 270°
Scale drawing
A diagram which is used to accurately represent real life objects.
Architects’ plans are scale drawings of buildings.
Important things to remember:
1) When calculating the bearings you need to start on the north line
2) When constructing the perpendicular bisector of a line make sure to leave in construction lines
Worked examples
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