# Transformations of the Unit Square in the x - y Plane

## Identifying Transformations

• Understand that transformations can be recognised by the image of the unit square under the transformation.
• Scaling is marked by stretching or shrinking of the unit square and is caused by a scalar factor in the matrix.
• Rotation is recognised when the unit square is reoriented but maintains the same size and shape.
• A reflexion is notable if the image is a mirror version of the unit square.
• A shear is typified by the square appearing to be pushed to one side.

## Properties of the Unit Square

• Note that the unit square in the x-y plane motivates the concept of any square with sides parallel to the axes.
• Be aware that the unit square refers to a square of side length 1, whose bottom-left corner is at the origin.
• Remember that transformations can be applied to the unit square to help visualise matrix transformations.

## Working with Transformations

• Understand that transformation of the unit square can be represented using matrices to change the position of the points.
• Learn to multiply the coordinates of the square by the matrix to find the transformed coordinates. This applies to transformations including enlargement, reflections, rotations and shearing.
• Be confident manipulating the unit vectors i (pointing in the direction of one unit on the x-axis) and j (pointing in the direction of one unit on the y-axis).

## Analysing the Impact of Transformations

• Understand that an unchanged unit square signifies the identity matrix.
• A negative determinant of the transformation matrix indicates a reflexion has occurred.
• Keep in mind that the determinant of a transformation matrix gives the area scale factor.
• Remember, if the determinant is 1 or -1, the transformation is area-preserving (i.e., the area of the unit square remains the same).