Post on 13-Jan-2016
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