RIC-1069 Maths terms and tables

Symmetry
Reflectional symmetry
This is the correspondence, in size, form and arrangement, of parts of an
object or figure on opposite sides of a point, line, axis or plane.
2-D: Lines of symmetry
One line of symmetry
Asymmetry
No lines of symmetry
More than one line of symmetry
3-D: Planes of symmetry
The diagram below shows one
of the planes of symmetry of a
cube, which has a total of nine
planes of symmetry.
Rotational symmetry
An object or figure has rotational symmetry if it appears to retain its original
orientation after rotating through some fraction of a complete turn about
a fixed point.
This shape
has an order
of rotation
of 4, as in
one full 360º
rotation,
there are 4
places where
it looks the
same as the
original.
x
x
x
x
This shape
has an order
of rotation
of 3, as in
one full 360º
rotation,
there are
3 places
where it
looks the
same as the
original.
Note: If a shape can only
be rotated once to return
to its original position, it
does not have rotational
symmetry. There is no
order of rotation of 1. For
example, the triangle
below does not have
rotational symmetry.
3-D: Axes of symmetry
The diagram below shows one of the
axes of symmetry of a tetrahedron. It
has an order of rotational symmetry
of three about the axis shown.
R.I.C. Publications ® www.ricpublications.com.au Maths terms and tables
101