The sum of interior angles in a quadrilateral is 360˚. In a square or rectangle, each interior angle is 90˚. In irregular quadrilaterals, each angle is a different size. To find a missing angle ...

In a sort of progression from easy to hard mode, the trials featured such quadrilaterals as the classic square, rhombus, isosceles trapezoid, right hinge (shown above), and an arbitrary irregular ...