Reflecting a Shape in y = x Using Cartesian Coordinates
(KS3, Year 7)

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A shape can be reflected in the line y = x. If point on a shape is reflected in the line y = x, the x-coordinate becomes the y-coordinate and the y-coordinate becomes the x-coordinate. The image below shows a point on a shape being reflected in the line y = x:

reflect a shape in y=x_cartesian_coordinates

reflect a shape in y=x_cartesian_coordinates

The point A has Cartesian coordinates (2, 3).
The reflected point A' has Cartesian coordinates (3, 2). The x-coordinate of A (2) has become the y-coordinate of A'. The y-coordinate of A (3) has become the x-coordinate of A'.

How to Reflect a Shape in y = x Using Cartesian Coordinates

Reflecting a shape in the line y = x using Cartesian coordinates is easy.

Question

Reflect the shape below in the line y = x. reflect a shape in y=x_cartesian_coordinates_example

Step-by-Step:

1

Find the Cartesian coordinates of each point on the shape. Write the x-coordinates and y-coordinates of each point.

Point	x-coordinate	y-coordinate
A	1	6
B	4	5
C	1	4

2

Find the Cartesian coordinates of the reflected points. Swap the x-coordinate and the y-coordinate of the original point.

Point	x-coordinate	y-coordinate	Point	x-coordinate	y-coordinate
A	1	6	A'	6	1
B	4	5	B'	5	4
C	1	4	C'	4	1

3

Plot the reflected points and draw in the shape.

Answer:

We have reflected the shape in the line y = x.

reflect a shape in y=x_cartesian_coordinates_answer

A Formula to Reflect a Point in y = x Using Cartesian Coordinates

In general, we write Cartesian coordinates as: cartesian_coordinate_point

x is the x-coordinate. y is the y-coordinate. x and y can taken any number. The reflected point has Cartesian coordinates:

cartesian coordinate point reflected in y=x