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.
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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)
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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)
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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))
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Regular pentagon
(All regular polygons have the same number of lines of symmetry as the number of sides)
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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.
