Diagonals of a rhombus are perpendicular and bisect each other. This means this rhombus is composed of four right triangles with legs of length 6 cm and 8 cm, with their hypotenuses forming the perimeter of the rhombus. The Pythagorean theorem a^2+ b^2 = c^2 can be used to find the length of the hypotenuse. 6^2+8^2 = 36+64 = 100. The square root of 100 is 10, so the length of a side of the rhombus is 10 cm.