1. Symmetry

Introduction
Symmetry is quite a common term used in day to day life. When we see certain figures with evenly balanced proportions, we say, “They are symmetrical”.
Suppose we could fold a picture in half such that the left and right halves match exactly then the picture is said to have line symmetry (Fig). We can see that the two halves are mirror images of each other. If we place a mirror on the fold then the image of one side of the picture will fall exactly on the other side of the picture. When it happens, the fold, which is the mirror line, is a line of symmetry (or an axis of symmetry) for the picture.

When we fold them along the dotted line, one half of the drawing would fit exactly over the other half.
 

Reflection & Mirror Symmetry

Reflection Symmetry
If we draw a vertical line at the middle, the portions on either side of the line are identical. Similarly, in nature we find many flowers, leaves, etc., that have two identical sides if we draw a line through the middle of them.

Mirror  Symmetry
Reflection symmetry is the symmetry with respect to reflection. If a mirror is placed along the line at the middle, the half part of the figure reflects through the mirror creating the remaining identical half. In other words, the line where the mirror is placed divides the figure into two identical parts  they are of the same size and also every specific part on one side of the line will have its reflection exactly at the same distance on the other side. Thus, it is also known as mirror symmetry or mirror image symmetry.
Here is a picture showing the reflection of the English letter M. You can imagine that the mirror is invisible and can just see the letter M and its image.

 

Asymmetrical figure

Asymmetrical figure
Some  objects and figures have no line of symmetry, a scalene triangle is not symmetrical. We can say that a scalene triangle is asymmetrical. The irregular shapes have no line of symmetry.

Figures with Multiple (more than two) Lines of Symmetry
Some objects and figures have more than one line of symmetry.

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