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Geometry Transformations

Reflectional Symmetry

A figure has reflectional symmetry or symmetry about a line if a line can be drawn through it, dividing it into two parts that are the same but facing in opposite directions.

Find the lines of reflectional symmetry.

 Equilateral triangle (An equilateral triangle has three lines of symmetry. Each line of symmetry is drawn from a vertex of the triangle to the midpoint of the opposite side) Square (A square has four lines of symmetry. Two are the diagonals. The other two are each drawn from the midpoint of a side to the midpoint of the opposite side) Rectangle (A rectangle that is not a square has two lines of symmetry. Each is drawn from the midpoint of a side to the midpoint of the opposite side. (The diagonals of a rectangle are not lines of symmetry)) Regular pentagon (All regular polygons have the same number of lines of symmetry as the number of sides)

Following are facts about line symmetry:

• A line of symmetry is the line that divides the figure into two identical parts that face in opposite directions.
• If a figure is folded along a line of symmetry, each part of the figure will coincide with the other part.
• Some figures have no lines of symmetry. A scalene triangle is one example.

Draw an image with horizontal, but not vertical, reflectional symmetry.

Letter "B" has horizontal reflectional symmetry but not vertical.