Name: Line and Rotational Symmetry
Uploaded: 2019-07-19
Duration: 11 min 22 s
Description: Do you know that symmetry is something that has exactly equal parts? Let us learn more about line and rotational symmetry by watching this video.

Question

Match each figure with the number of lines of symmetry it has.

Figure	Number of lines of symmetry
Rectangle	Infinite
Square	Four
Isosceles Triangle	Two
Equilateral triangle	One
Rhombus	Three
Kite	One
Parallelogram	Two
Circle	Zero

Accepted Answer

A figure which is identical on both sides of a line is said to be symmetrical about the line. The line about which the figure is symmetrical is called the line of symmetry or the axis of symmetry.
Consider the rectangle as shown below

A horizontal line through the midpoints of the two vertical sides and a vertical line through the midpoints of the two horizontal sides.
Hence, a rectangle has $2$ lines of symmetry.

Consider the square shown below,

A square is symmetrical about each one of its diagonals and the lines joining the midpoints of the opposite sides.
Thus, a square has $4$ lines of symmetry.

Consider the isosceles triangle

In an isosceles triangle, two sides are equal. So, the line of symmetry for an isosceles triangle goes through $1$ vertex which formed by a pair of equal sides.
Thus, an isosceles triangle has $1$ line of symmetry.

Consider the equilateral triangle as shown below

In the equilateral triangle, all sides are equal. So, lines of symmetry for an equilateral triangle go through $3$ vertices, each formed by a pair of equal sides.
Therefore, an equilateral triangle has $3$ lines of symmetry.

Consider the rhombus as shown below

A rhombus is symmetrical about each of its two diagonals.
Thus, a rhombus has $2$ lines of symmetry.

Consider the figure of kite as shown below

A kite is a quadrilateral with two different pairs of adjacent sides that are equal in length.
Thus, it has only one line of symmetry.

Here is a parallelogram,

We will not be able to fold this figure along any line, in such a way that the two halves are mirror images of each other.
So, it has no line of symmetry i.e., zero line of symmetry.

In a circle, a line that goes through its center is a line of symmetry i.e., every diameter of a circle is a symmetry line for the circle.
Thus, there are infinite lines of symmetry for a circle.

Hence, the required table is as shown below

Figure Answer (Number of lines of symmetry)

Rectangle Two

Square Four

Isosceles Triangle One

Equilateral triangle Three

Rhombus Two

Kite One

Parallelogram Zero

Circle Infinite

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