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Maths

Transformations

Reflections in y = x, y = - x, y = c and x = c

In your exam, you might have to reflect a shape in a given line. You will need to remember that:

y = c describes a horizontal line through c.

x = c describes a vertical line through c.

A point and its image are always the same perpendicular distance from the mirror line. Have a look at the reflections below:

The object is triangle ABC

Look at this table:

 

 Coordinates of verticesReflection in y = xReflection in y = -x
A(1, 2)(2, 1) (-2, -1)
B(1, 5) (5, 1) (- 5, -1)
C(3, 2) (2, 3) (-2, -3)

Can you see the pattern?

After a reflection in the line y = x, the x and y coordinates swap over.

After a reflection in the line y = - x, the x and y coordinates swap over and change signs.

Activity

Creat your own reflections using the transformations activity.

Back to Geometry and measures index

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