Geometry
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Features
Features, sometimes called attributes, are visual characteristics of a shape or object that can be seen.
Properties
Shapes and objects have distinguishable characteristics and are named because of their properties.
The properties of two-dimensional (2D) shapes typically include relationships among the number, length and relative position of sides, as well as the number and angle of corners, lines of symmetry, convexity and concavity.
The properties of three-dimensional (3D) objects typically include the shape and relative position of faces, surfaces, edges and vertices (corners).
Classes (i.e. categories) of shapes are defined by their properties, which are relationships among features of similar shapes.
Properties are relationships connecting characteristics of shapes or objects.
Some properties are defining; that is, they describe what a shape must have to belong to a class.
Classification
Classification involves establishing criteria to group shapes by their common properties.
Classification is about working with relationships among properties, where individual shapes are examples of the classes and are hierarchical.
Orientation
Orientation is the position of a shape on a plane or an object in space, in particular the direction that the features of the shape or object are facing.
The orientation of a shape remains unchanged as it is translated (i.e. shifted) or enlarged, but changes when a shape is reflected or rotated through an angle not equal to 360°.
Transformation
Transformation is the change in the size, shape or position of a shape or object.
Isometric transformations
Isometric transformations include translations, rotations and reflections. Note: these do not change the size or proportions of a shape or object.
Translation (slide): the movement of a shape to a new position. The length of sides and angles remain unchanged.
Rotation (turn): a change to the position of a shape by rotating it about a fixed point through a given angle. The point may be inside or outside the shape.
Reflection (flip): a change to the position of a shape by reflecting it along a mirror line. The line may run through the shape or be external to it.
Non-isometric transformations
Non-isometric transformations include enlargements and reductions (dilations).
A dilation is a change to the size of a shape about a point. The lengths of the sides and/or the angles are changed.
Point of view
Objects appear differently depending upon the position from which they are viewed.
Symmetry
A shape has symmetry if it maps onto itself by a transformation, particularly through reflection and/or rotation.
Reflective symmetry
In reflective symmetry, the locations of the mirror are called lines of symmetry.
Rotational symmetry
In rotational symmetry, the point is known as the centre of rotation and the angle of rotation is the measure of turn that maps the shape onto itself.
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Important concept knowledge list
For descriptions and examples on the list below, please go to pages 38-40 on the above link.
Geometric reasoning
Point
Line
Ray
Plane
Two-dimensional shape
Polygon
Three-dimensional object
Polyhedron
Net
Congruence
Similar shapes
Regular shapes
Tessellation
Apex
Cross-section
Truncated objects
Right object
Oblique object
Angle
Adjacent angle
Complementary angles
Supplementary angles
Vertically-opposite angles
Angles at a point
Parallel lines
Transversals
Corresponding angle
Alternate angle
Co-interior angle
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Position
The position of an object on a plane or in space can be specified and described relative to a reference point.
Direction
The direction (i.e. movement) of an object can be described relative to its starting position and surrounding landmarks.
Orientation
The orientation of an object can be described in relation to a reference direction.
Usually the reference direction is a compass point or bearing, or axes on a Cartesian plane.
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Visual representations
The location of objects on a plane and/or in space can be visually represented; each representation has particular purposes and ways in which they are read and interpreted.
Visual representations include diagrams, plans, grids, maps, directories and networks.
Coordinate systems
A coordinate system is a system used to locate the position or direction of an object on a plane or in space relative to the distance from an origin.
Grid reference
An alpha-numeric grid reference defines a region on a map.
An ordered pair reference defines a point, rather than a region, on a map or Cartesian plane.
Compass points
Cardinal direction
A cardinal direction is a bearing described by north, south, east and west, and is commonly denoted by the direction’s initial.
The four main points on a compass are:
• north (N) – 0° or 360°
• east (E) – 90°
• south (S) – 180°
• west (W) – 270°.
Inter-cardinal direction
Inter-cardinal points can also be used:
• north-east (NE) – 45°
• south-east (SE) – 135°
• south-west (SW) – 225°
• north-west (NW) – 315°.
Other inter-cardinal points include:
• north-north-east (NNE) – 22.5°
• east-north-east (ENE) – 67.5°
• east-south-east (ESE) – 112.5°
• south-south-east (SSE) – 157.5°
• south-south-west (SSW) – 202.5°
• west-south-west (WSW) – 247.5°
• west-north-west (WNW) – 292.5°
• north-north-west (NNW) – 337.5°.
Bearings
A bearing is the angle between north and another landmark as taken from a fixed point.
The angle is measured in a clockwise direction.
BOLTSS
BOLTSS (i.e. border, orientations, legend, title, scale and source) is standard information to include on a map:
border – the limits of the area covered by a map
orientation – an indication of north
legend – symbols on the map that represent natural or artificial features on the ground; legends are sometimes referred to as ‘keys’ as they ‘unlock’ the meaning of the symbols
title - the name of the map, identifying the geographic area that it covers
scale - a ratio indicating distance on a map in relation to distance on the ground
source - where the information on the map originated.
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The overarching key ideas have a broad application and are fundamental to enabling students to connect concepts across all areas of mathematics.
Consequently, they need to be considered by educators when developing each unit of work.