Geometry: a parallelogram with perpendicular diagonals bisect each other.

Question

in a parallelogram ABCD with perpendicular diagonals which bisect each other. Is it also true at the bisection of the diagonal lines all the angles are 90 degrees

Answer 1

"Parallelogram" is TMI (too much information); don't get distracted by the outside shape.

If the two diagonals are PERPENDICULAR, then the four angles at the point of intersection are each 90°.