We know in rhombus diagonals bisect each other at right angle.

In ΔAOB

AO = , BO =

Using pythagorous theorem in ΔAOB

AB² = AO² + BO²

AB² = 6² + 8²

AB² = 36 + 64

AB² = 100

AB = = 10cm

Therefore each side of a rhombus is 10cm.