Simple Triangle/rectangle problem

[letmedanz]

hi people,

got a simple question here..
assuming it is simple it seems so... but has been a long time since geometry, so looking for help :)

assuming only the length of a diagonal of a rectangle is known (say 20"), is it possible to find the length & breadth..?

stating to be a rectangle, as there is no clarity if this is a square or not...

any help will be appreciated!

[mathwonk]

does the diagonal length of a piece of paper determine the exact size of the paper?

are two right triangles congruent if they have the same diagonal? I.e. does one side and one angle determine a triangle?

do you know pythagoras theorem?