Teach GCSE Maths

Lines ofLines ofSymmetrSymmetr

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Teach GCSE Maths

Lines of Lines of SymmetrySymmetry

© Christine Crisp

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These shapes all have at least one line of symmetry.

If we could fold a shape along a line of symmetry the two parts would exactly fit.

These shapes all have at least one line of symmetry.

If we could fold a shape along a line of symmetry the two parts would exactly fit.

Each of these 3 shapes has a special name. Can you tell your partner what they are?

Rectangle

Isosceles triangle

Kite

e.g.1 How many lines of symmetry do these shapes have?

Parallelogram

There are no lines of symmetry

We can show a diagonal is not a line of symmetry by reflecting half the parallelogram in the diagonal.

The reflected triangle does not match the other half of

the parallelogram.

Answers:

(a)

(b)

(c)2

4

e.g.2 Complete the diagrams so that the dashed line is a line of symmetry

Ans:

1. How many lines of symmetry do these shapes have?

EXERCISE

Square

Rectangle

1. How many lines of symmetry do these shapes have?

EXERCISE

Square

Rectangle

14

Ans:

The diagonals of a rectangle are not lines of symmetry.

2

2

2. Copy and complete the table for the number of lines of symmetry of the quadrilaterals listed.

EXERCISE

1

0

2

2

4

Kite

Other parallelograms

Rectangle

Rhombus

Square

Number of lines of symmetry

ShapeAns:

SUMMARY

A line of symmetry is like a mirror line.

If we could fold on a line of symmetry the 2 parts would fit together exactly.

A “general” parallelogram has no lines of symmetry. The special ones with equal sides, the square and rhombus, have 4 and 2 lines of symmetry respectively.

Square4

Rhombus

2