The line y=x is shown in the following diagram:
We can find the notation used to make a reflection over this line by taking a point, for example:
We take the point (0,4) and reflect it across the line y=x. To make this reflection, the line y=x acts as a mirror in which we reflect the point, and we find that the reflected point is:
The new point after the reflection is the green point (4,0).
