Mathematics for IGCSE & O level - Transformations (Section 7 - No. 17)
What is the effect of reflecting an object over the line y = x?
The x and y coordinates swap.
The x coordinate is multiplied by -1.
The y coordinate is multiplied by -1.
The x and y coordinates are not affected.
Explication
When reflecting over y=x, the coordinates (x,y) become (y,x).