You can
put this solution on YOUR website!If we cut the rectangle in half along the diagonal, we get the following triangle:
Since the legs are

and

this means that

and
Also, since the hypotenuse is

, this means that

.

Start with the Pythagorean theorem.

Plug in

,

,

Square

to get

.

Square

to get

.

Subtract

from both sides.

Combine like terms.

Take the square root of both sides. Note: only the positive square root is considered (since a negative length doesn't make sense).

Simplify the square root.
================================================================
Answer:
So the solution is

which means that the other side length is 16 mm