well, for a <u>square</u> the diagonals do bisec each other, they cut each other in two equal halves.
and for a <u>rectangle</u>, they do as well, mind that a square is a rectangle with all equal sides anyway.
wait just a second, for a <u>parallelogram</u>, they do bisect as well.
hold the mayo, for a <u>rhombus</u> they do too, what the dickens is going on?
well, what do they all those have in common?
they're all quadrilaterals, but, they all have two pairs of parallel sides.
mind you that, a <u>kite</u> is also a quadrilateral, however, it doesn't have all equal sides and the diagonals do not bisect each other, and yes, it has no pairs of parallel sides.