If you divide a 4 inch by 8 inch rectangle from corner to corner what new shapes would you get? are they congruent? why or why not ?

I have already answerd this on a other question. So i am pasting my other answer.
You get two congruent right triangles when you divide a rectangle diagonally. 

(This is one way to show that the area of each of those triangles is 1/2*base*height. Rectangle area = (4 in)(8 in) = 32 in2. Triangle area = (1/2)(4 in)(8 in) = 16 in2.)

Maybe fx = lxl because of the way the x is positioned is that what he