Symmetry & Shapes (Edexcel GCSE Maths: Foundation): Flashcards
Exam code: 1MA1
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Define a line segment.
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Cards in this collection (18)
Define a line segment.
A line segment is the part of a line between two end points, unlike a line itself, which carries on forever in both directions.
A segment starting at
and ending at 
is written as 
.On a diagram, what do arrows drawn on two lines mean, and what do tick marks mean?
Arrows show that the lines are parallel; tick marks show that the lines are equal in length.
Where a diagram has a second, separate pair of each, double arrows and double ticks are used to keep the two pairs apart.
What does it mean for two lines to be perpendicular?
They intersect at right angles, meaning the angle between them is 90°.
On a diagram this is marked with a small square at the point where they cross.
Complete the two descriptions by filling in the missing names:
An angle smaller than 90° is called an
angle.An angle between 90° and 180° is called an
angle.The completed descriptions are:
An angle smaller than 90° is called an acute angle.
An angle between 90° and 180° is called an obtuse angle.
True or False?
An angle of 200° is called a reflex angle.
True.
Any angle greater than 180° but less than 360° is reflex.
An angle of exactly 180° is a straight angle, so reflex angles pick up where that leaves off.
What is rotational symmetry?
A shape is said to have rotational symmetry if, during a 360° rotation about its centre, it looks the same as it did in its original position.
What is meant by the order of rotational symmetry?
The order of rotational symmetry refers to the number of times a shape looks the same as it is rotated 360° about its centre.
True or False?
A shape can have order 0 rotational symmetry.
False.
A shape can never have order 0 rotational symmetry.
A shape is said to have no rotational symmetry when the order of rotational symmetry is 1, i.e. it only looks like its original position when it has been rotated through the full 360°.
How can tracing paper be used to help work out the order of rotational symmetry of a shape?
You can use tracing paper to help you work out the order of symmetry for a particular shape by doing the following:
Sketch the shape onto the tracing paper.
Draw an arrow pointing upwards on the tracing paper.
Place your pencil in the centre of the shape and rotate the tracing paper until the arrow is pointing upwards again (360º).
Count how many times the shape on the tracing paper maps over the shape on the paper beneath exactly; this is the order of rotational symmetry.
What is line symmetry?
A shape is said to have line symmetry when one half of the shape is a mirror image of the other half.
What is a line of symmetry?
A line of symmetry is a line across which a shape can be folded or reflected so that the two halves match exactly.
True or False?
A line of symmetry is also known as a line of reflection.
True.
A line of symmetry is also known as a line of reflection.
It can also be called a mirror line.
How can tracing paper be used to help sketch the reflection of a shape?
You can use tracing paper to help you sketch the reflection of a shape:
Trace the shape and the line of symmetry on the tracing paper.
Flip the paper over the line of symmetry.
The traced image will now be in its reflected position.
What is a plane of symmetry in a 3D shape?
A plane of symmetry in a 3D shape is a plane (flat 2D shape) that splits a 3D shape into two congruent (identical) halves that are mirror images of each other.
How many planes of symmetry does a cube have?
A cube has 9 planes of symmetry.
How many planes of symmetry does a cuboid have?
A cuboid has 3 planes of symmetry.
How many planes of symmetry does a square-based pyramid have?
A square-based pyramid has 4 planes of symmetry.
True or False?
A cylinder has infinite rotational symmetry.
True.
A cylinder has infinite rotational symmetry about the axis that runs through the centre point of both circular faces.
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