Transformations

2) The equation of the line of symmetry

To describe a reflection on a grid, the equation of the mirror line is needed.

Reflect the shape in the line x=-1.

Triangle ABC on a set of co-ordinates

The line x=-1 is a vertical line which passes through -1 on the x-axis.

Triangle (ABC) reflected in the line, x=-1
Question 1

Describe the transformation of the shape ABC.

Triangle (ABC) reflected in the line, y=1

Answer: The line is a horizontal line which passes through 1 on the x-axis. The shape has been reflected in the line y=1.

Question 2

Reflect the shape in the line y=x .

Answer: The equation of a straight line graph has the form of y=mx+c , where m is the gradient and c is where the line crosses the y-axis.

The line y=x has a gradient of 1 and crosses the y-axis at (0,0).

Triangle (ABC) reflected in the line, y=x
Question 3

Describe the transformation of the shape ABC.

The mirror line has a gradient of -1 and crosses the y-axis at (0,0). The shape has been reflected in the line y=-x .


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