So, if you take a rhombus, then call the bottom left hand corner $A$, the top left hand corner $B$, the top right hand corner $C$, and the bottom right hand corner $D$. Then draw the two diagonals.
The angle of the bottom left hand corner is $60°$. The side lengths are $10$ cm. Call the point where the diagonals bisect each other $X$. I have to find the distance of $AX$.