**11.1.3 Reflection**

**1.**A reflection is a transformation which reflects all points of a plane in a line called the axis of reflection.

**2.**In a reflection, there is no change in shape and size but the orientation is changed. Any points on the axis of reflection do not change their positions.

*Example 3***:**

**11.1.4 Rotation**

**1.**A

**rotation**is a transformation which rotates all points on a plane about a fixed point known as the centre of rotation through a given angle in a clockwise or anticlockwise direction.

**2.**In a rotation, the shape, size and orientation remain unchanged.

**3.**The centre of rotation is the only point that does not change its position.

Example 4Example 4

**:**

Point

*A*(3, –2) is rotated through 90^{o}clockwise to*A’*and 180^{o}anticlockwise to*A*respectively about origin._{1}State the coordinates of the image of point

*A*.

SolutionSolution

**:**

Image

*A*’ = (–2, 3)

Image

*A*_{1 }= (–3, 2)**11.1.5 Isometry**

**1.**An isometry is a transformation that preserves the shape and size of an object.

**2.**Translation, reflection and rotation and a combination of it are isometries.

**11.1.6 Congruence**

**1.**

**Congruent figures**have the same size and shape regardless of their orientation.

**2.**The object and the image obtained under an isometry are congruent.