 Hello and welcome to the session. In this session, we will learn about symmetry. Symmetry is quite a common term that we use in day-to-day life. When we see certain figures with evenly balanced proportions, we say that they are symmetrical figures. Let's consider the circle with a line dividing the circle into two halves. As you can see, these two halves of the circle are identical. So, these both are symmetrical figures and this line is said to be the line of symmetry. So, we have that a line that divides a figure into two identical parts is called the line of symmetry or we can also say an axis of symmetry. The two halves in this case are mirror images of each other. We know that a figure may have no line of symmetry, only one line of symmetry, two lines of symmetry or multiple lines of symmetry. Now, let's consider some examples for each. An example of a figure with no line of symmetry can be a scalene triangle. So, we have taken a scalene triangle and a line dividing this triangle into two parts. Now, as you can see that these two parts are not identical, so we see that this line is not the line of symmetry for this triangle. So, we say that the scalene triangle does not have a line of symmetry. Next, we have a figure with only one line of symmetry can be an isosceles triangle. This is an isosceles triangle. We have drawn a line dividing this figure into two parts. It's visible that these two parts are identical, so this line is the line of symmetry. Now, let's draw another line. When we draw this line, you can see that these two parts are not identical, hence this line is not the line of symmetry. Similarly, this third line is also not the line of symmetry as this does not divide the triangle into two identical parts. So, this isosceles triangle has only one line of symmetry. Next, a figure with two lines of symmetry is rectangle. This is a rectangle and we have drawn a line dividing this rectangle into two parts. Now, as you can see these two parts are identical, so we see that this line is the line of symmetry for this rectangle. We have drawn this horizontal line also. Now, this line also divides this rectangle into two equal parts, so this line can also be considered as the line of symmetry. So, we see that a rectangle has two lines of symmetry. Now, a figure with three lines of symmetry is equilateral triangle. This line divides this equilateral triangle into two equal parts, so this is a line of symmetry. This line also divides this triangle into two identical parts, so this is also a line of symmetry. This third line also divides the triangle into two identical parts, so this is also the line of symmetry. Hence, we have that equilateral triangle has three lines of symmetry. Now, let's discuss about reflection and symmetry. Line symmetry is closely related to mirror reflection. This is the picture showing the reflection of the letter m. This is the main object, this is the mirror and this is the image. As you can see in this, the object and its image are symmetrical with reference to the mirror line. We can also say that the image is the reflection of the object in the mirror line and as you can notice that there is no change in the lens and angles of the object and the image. When dealing with mirror reflection, we have to take into account the left-right changes in orientation. This completes the session. Hope you have understood the concept of symmetry, the lines of symmetry and reflection and symmetry.