5.2.2
Rotations
Describing Transformations
Describing Transformations
Transformation can be used to describe how a shape or point moves on coordinate axes.


Object and image
Object and image
- The original shape or point before a transformation is known as the object.
- The new shape or point after a transformation is known as the image.


Describing a rotation
Describing a rotation
- An angle of rotation and a centre of rotation are required to describe a rotation.
- The angle of rotation tells you how much the object rotates by.
- You can often tell the angle of rotation by comparing the orientation (way round) of the object and image.
- The centre of rotation tells you where the rotation centres around.


Angle of rotation
Angle of rotation
- Look at the orientation to work out the angle of rotation.


Centre of rotation
Centre of rotation
- Find the centre of rotation using tracing paper.
- Draw around the object and place your pencil where you think the centre of rotation is.


Centre of rotation cont.
Centre of rotation cont.
- Use trial and error until you rotate the object on the tracing paper and it makes the image.
- This takes a lot of practice to get good at but it gets easier the more you try it.
Rotations
Rotations
Using x and y coordinates, we can rotate shapes on a graph.


90o rotation
90o rotation
- Shape A has rotated 90o anti-clockwise to become shape B, with its centre of rotation at the origin.
- The x and y coordinates for shape A and B swapped.
- The x coordinates have changed sign but the y coordinates have not.


180o rotation
180o rotation
- Shape A has rotated 180o anti-clockwise to become shape B, with its centre of rotation at the origin.
- The x and y coordinates for shape A and B are the same but have changed sign.


270o rotation
270o rotation
- Shape A has rotated 270o clockwise to become shape B, with its centre of rotation at the origin.
- The x and y coordinates for shape A and B swapped.
- The y coordinates have changed sign but the x coordinates have not.


Clockwise and Anti-clockwise
Clockwise and Anti-clockwise
- A positive angle of rotation is defined as the angle of rotation in an anti-clockwise direction
- A negative angle of rotation is defined as the angle of rotation in a clockwise direction.
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
Jump to other topics
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
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