When a point (x,y) is reflected across the line y = x:
We have the transformation rule:
[tex](x,y)\to(y,x)[/tex]That is, the x-coordinate and y-coordinate change places.
For example:
If we reflect the point (2,5) over y=x, the image of the given point will be:
[tex](5,2)[/tex]If the coordinate has a positive x and negative y, the transformation will be:
[tex](x,-y)\to(-y,x)[/tex]