Question

How do I memorize theorems and postulates for a Geometry test tomorrow on properties of quadrilaterals?

Answer 1

try to understand the logic behind the theorems, you don't necessary have to remember the proofs, just the idea behind it.

Answer 2

Actually, the theorems and postulates fit into a beautiful whole.
A trapezoid has only 1 parallel side. The only noteworthy "beautiful" trapezoid is the isosceles trapezoid, which like the isosceles triangle, which has congruent bases and congruent diagonals.
A parallelogram has 2 parallel sides. They are congruent. The angles are congruent. The diagonals bisect. A rectangle is just a parallelogram, so it has all the properties of a parallelogram but additional property is 4 congruent (right) angles so the diagonals are congruent. A rhombus is another parallelogram with 4 congruent sides, so it has all properties of parallelogram with additional property of perpendicular diagonals. A square, the most beautiful quadrilateral has 4 right angles and 4 congruent sides, so it has all properties of parallelogram, rectangle, and rhombus.
And a kite is like a rhombus, just not as "pretty" because it only has 2 pairs of congruent sides. So the diagonals are perpendicular but not congruent.
So when you look past the panic of having to remember all the theorems, the properties of quadrilaterals actually fit into a beautiful pattern. I'm sure there's a KhanAcademy video that's gonna explain all the properties of quadrilaterals anyway.