The word

**symmetry**comes from the Greek word**symmetros***,*which means even.
A figure has

**line symmetry**if a line can be drawn dividing it into two identical parts. The line is called the**line of symmetry**or**axis of symmetry**.**Line symmetry**is also known as

**reflection symmetry**because a mirror line resembles the

**line of symmetry**, where one half is the mirror image of the other half. Remember, while looking at a mirror, an object placed on the right appears to be on the left, and vice versa.

- For a
**line segment**, the**perpendicular bisector**is the**line of symmetry**. - For an
**equilateral triangle**, the**bisectors of the internal angles**are the**lines of symmetry**. - For a
**square**, the**lines of symmetry**are the**diagonals**and the**lines joining the mid-points of the opposite sides**. - The
**lines of symmetry**of a**rectangle**are the lines joining the**mid-points**of the**opposite sides**. - The
**line of symmetry**of an**isosceles triangle**is the**perpendicular bisector**of the non-equal side. - A
**scalene triangle**, in which all the**sides are of different lengths,**doesn’t have any**line of symmetry**.

#### Regular polygon:

- A
**polygon**is said to be a**regular polygon**if all its sides are equal in length and all its angles are equal in measure. If a polygon is not a**regular polygon**, then it is said to be an**irregular polygon**. **Regular and irregular polygons**have**lines of symmetry**. An**equilateral triangle**is regular because each of its sides has the same length, and each of its angles measures sixty degrees.- The number of
**lines of symmetry**in a**regular polygon**is equal to the number of sides that it has. - A
**pentagon**has five**lines of symmetry.** - Similarly, a
**regular octagon**has eight sides, and therefore, it will have eight**lines of symmetry,**while a**regular decagon**has ten sides, so it will have ten**lines of symmetry**.

#### Irregular polygon:

- Most
**irregular polygons**do not have**line symmetry**. However, some of them do. Look at the**rectangle**and the**isosceles triangle**. A**rectangle**has two**lines of symmetry,**and an**isosceles triangle**has one**line of symmetry**. - Some letters have
**line symmetry**. - The letters A, B, C, D, E, I, K, M, T, U, V, W and Y have
**one line of symmetry**. - The letter H overlaps perfectly both vertically and horizontally. So it has
**two lines of symmetry**. - Similarly, the letter X has
**two lines of symmetry**. - The letters F, G, J, L, N, P, Q, R, S and Z have
**no line of symmetry**.

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