A cuboid is sketch below.
Write down the formula by which we use the Pythagorean theorem to calculate the space diagonal 
of a cuboid, and from it express the diagonal of the base plane 
as the subject of the formula.
Write a formula with which we use the Pythagorean theorem to calculate the space diagonal of a cuboid, using the length a, the width b and the height c and express the width b of the cuboid as the subject of the formula.
