Topics Covered

8 key topics in this chapter

Angle Sum Property of Quadrilaterals

Types of Quadrilaterals

Properties of Parallelogram

Diagonals of Parallelogram

Conditions for a Parallelogram

Rectangle, Rhombus, Square

Mid-Point Theorem

Converse of Mid-Point Theorem

Study Resources

Formula / Rule	Expression
Quad Angle Sum	\(∠A + ∠B + ∠C + ∠D = 360°\)
Parallelogram: sides	\(AB = CD, AD = BC\)
Parallelogram: ∠s	\(∠A = ∠C, ∠B = ∠D\)
Parallelogram: ∠ sum	\(∠A + ∠B = 180° \; (\text{co-interior)}\)
Diagonals bisect	\(AO = OC, BO = OD\; (\text{O = intersection})\)
Rectangle diagonals	\(AC = BD\; (\text{equal diagonals})\)
Rhombus diagonals	\(AC ⊥ BD\; (\text{perpendicular diagonals})\)
Mid-Point Theorem	\(DE ∥ BC\; \&\; DE = BC/2\; (\text{D, E midpoints of AB, AC})\)

Angle sum of any quadrilateral = 360°. This follows by dividing into two triangles.

A parallelogram has: opposite sides equal and parallel, opposite angles equal, diagonals bisect each other.

A rectangle is a parallelogram with all angles 90°; a rhombus has all sides equal; a square is both.

Mid-Point Theorem: the segment joining midpoints of two sides of a triangle is parallel to the third side and half its length.