Hello RonYes, it is a rectangle.

A quadrilateral is a rectangle if all its angles are right-angles. Using the fact thatpis perpendicular tolandlis parallel tomis sufficient to prove thatpis perpendicular tom(corresponding angles equal). Three of the angles of ABCD are now known to be right-angles. Therefore the fourth is also a right-angle (angle sum of quadrilateral). Therefore ABCD is a rectangle.

Grandad