In a rhombus, the diagonals meet at right-angles, and they bisect each other, namely they cut each other in half, check the picture below.
thus we can use the pythagorean theorem to get one side, keeping in mind that, slanted as it may be, all sides in a rhombus are equal in length.
thus we can use the pythagorean theorem to get one side, keeping in mind that, slanted as it may be, all sides in a rhombus are equal in length.