(i)
The locus of the point in a rhombus \[ABCD\]which is equidistant from \[AB\text{ }and\text{ }BC\] will be the diagonal \[BD\]of the rhombus.
(ii)
The locus of the point in a rhombus \[ABCD\]which is equidistant from \[B\text{ }and\text{ }D\]will be the diagonal \[AC\]