6th Grade Math Textbook, Progress

Symmetry

10-15

When figures can be reflected or rotated and the result is

the original figure, these figures have symmetry.

Study these examples.

The word has reflection

symmetry.

The number has rotational

(180°) symmetry and point

symmetry.

The figure has reflection,

rotational, and point

symmetry.

Reflection Symmetry Rotational Symmetry Point Symmetry

Types of Symmetry

A figure has reflection

symmetry if a line, called a

line of symmetry, can be

drawn through the figure

so that the part of the

figure on one side of the

line is the mirror image of

the part on the other side.

A figure has rotational

symmetry if the figure

coincides with itself when

rotated in either direction

n°, where nis less than a

full turn (n
360°), about

a fixed point.

A figure has point

symmetry if there is a

central point so that the

part of the figure on one

side of the central point is

the reflection of the part

on the other side.

180°-rotational symmetry

is also point symmetry.

horizontal

line of

symmetry

vertical

line of

symmetry

vertical, horizontal,

and diagonal

lines of symmetry

diagonal

line of

symmetry

T T OO I96I

72 °( -turn)

rotational symmetry

1

5

72 ° 72 °

72 ° 72 °

72 °

120 °( -turn)

rotational symmetry

1

3

120 °

120 ° 120 °

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