Subject: Compulsory Maths
The dotted line which is the half part of each shape to one side of a dotted line is the mirror image of the other parts is called the line of symmetry . In another word, it is also called the axis of symmetry , so the figure is said to have bilateral symmetry or to be symmetrical by reflection in the dotted line and a line of symmetry shape can be turned so as it exactly into its outline.
Rotational symmetry
When a shape can be mapped onto itself by a rotation of less than a complete turn (360o) about a point the shape is said to have a rotational symmetry .
Order of rotational symmetry
When the shape is rotated through a half -turn it can be fitted to the original shape . It means , when it is rotated through 2 times half-turns , it reaches its original position .
\(\therefore\) It has rotational symmetry of order 2.
When the equilateral triangle is rotated through a \(\frac{1}{3}\) of turn 120o, it can fit over the original shape. When it is rotated through3 times \(\frac{1}{3}\) and then it will reach its original place.
\(\therefore\) It has rotational symmetry of order 3.
When the square is rotated through quarter-turn \(\frac{1}{4}\)of the turn 90o. Which can be fitted over the original shape . It means when it is rotated through 4time \(\frac{1}{4}\)of turn , it reaches its original position .
\(\therefore\) It has rotational symmetry of order 4.
Tessellation
A tessellation is known as tiling . It is covering of the plane with congruent geometrical shape un which a repeating pattern without leaving any gaps and without overlapping each other.The shape is polygons in it . It may be an equilateral triangle , regular hexagon or square . To make a tessellation :
Types of tessellation
What is Rotational symmetry?
When a shape can be mapped onto itself by a rotation of less than a complete turn (360°) about a point, the shape is said to have rotational symmetry.
Define line of symmetry.
When the half part of each shape to one side of the dotted line is the mirror image of the other part, the dotted part is called the line of symmetry.
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