New
New
Year 4

Diagonal lines of symmetry

I can reflect shaded squares and polygons in a diagonal line of symmetry.

New
New
Year 4

Diagonal lines of symmetry

I can reflect shaded squares and polygons in a diagonal line of symmetry.

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Lesson details

Key learning points

  1. A line of symmetry does not have to be vertical or horizontal. You can reflect shapes in a diagonal line of symmetry.
  2. You can reflect a shape by counting the position of each vertex and making a mark, and then joining the marks.
  3. Each vertex of a shape will be the same distance from the line of symmetry when it is reflected.

Keywords

  • Line of symmetry - If you were to fold a shape on its line of symmetry, both halves would match exactly.

  • Mirror line - Mirror line is another term to describe the line of symmetry.

  • Reflect - When you reflect a shape, you flip it over a mirror line or line of symmetry without turning it or changing the size.

  • Reflection - The reflection of a shape is the mirror image of a shape.

Common misconception

Children may try to reflect in a diagonal line but not at a 45 degree angle, leading to inaccuracies when marking each vertex.

Encourage children to work horizontally and then vertically, rather than trying to reflect in a diagonal line. Explore how this can be done in either order, orienting the paper, and notice how the same point will still be marked on the grid.

Allow children access to mirrors during this lesson and encourage them to use the mirror to check their work each time they have reflected a vertex, a pattern or a shape.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
Which of these images shows a correct reflection?
a)
b)
Correct answer: c)
Q2.
Which of these images is not a correct reflection?
a)
Correct answer: b)
c)
Q3.
Before reflection, this shape was a trapezium. Now, it is a __________.
An image in a quiz
octagon
Correct answer: hexagon
pentagon
Q4.
Before reflection, this shape was a right-angled triangle. Now, it is __________.
An image in a quiz
an equilateral triangle
Correct answer: an isosceles triangle
a scalene triangle
Q5.
Here are triangles that have been reflected with one of the sides touching the line of symmetry. Name the shapes that have been made.
An image in a quiz
Correct Answer:a),triangle

triangle

Correct Answer:b),kite

kite

Correct Answer:c),parallelogram

parallelogram

Q6.
True or false. When you reflect a square that has a side that touches the mirror line, it will create a larger square.
An image in a quiz
True
Correct answer: False

6 Questions

Q1.
Match each mirror line with its correct direction.
An image in a quiz
Correct Answer:a),horizontal

horizontal

Correct Answer:b),vertical

vertical

Correct Answer:c),diagonal

diagonal

Q2.
Which image shows a correct reflection?
An image in a quiz
a)
b)
Correct answer: c)
Q3.
True or false. This shape has been correctly reflected in a diagonal line of symmetry.
An image in a quiz
Correct answer: True
False
Q4.
Which image shows a correct reflection?
a)
Correct answer: b)
c)
Q5.
Here are quadrilaterals that have been reflected with one of the sides touching the line of symmetry. Name the shapes that have been made.
An image in a quiz
Correct Answer:a),kite

kite

Correct Answer:b),trapezium

trapezium

Correct Answer:c),rectangle

rectangle

Q6.
This shape has been reflected in a diagonal line of symmetry. The new shape is __________.
An image in a quiz
Correct answer: an octagon
a hexagon
a quadrilateral