The diagonal of a rectangle divides it into two congruent triangles.
True
In △ABC and △CDA, we have:
AB = CD (Opposite sides of a parallelogram)
BC = AD (Opposite sides of a parallelogram)
AC = AC (Common)
By SSS congruence condition, △ABC ≅ △CDA. So, the diagonal of the parallelogram divides it into two congruent triangles.