Parallelograms II — O/L Mathematics

What must I remember about Parallelograms II?

• Special parallelograms inherit all standard parallelogram properties while possessing distinct diagnostic characteristics.
• Rhombus: A parallelogram with four equal sides; diagonals bisect each other perpendicularly at 90° and bisect the corner interior angles.
• Rectangle: A parallelogram containing four right angles (90°); diagonals are equal in length and bisect each other.
• Square: Possesses all properties of both a rectangle and a rhombus (four equal sides, four right angles, diagonals equal and perpendicular bisectors).
• Area formulas: Rhombus Area = (1/2) × d₁ × d₂ (where d₁ and d₂ are diagonal lengths) = base × height.

Test yourself (1 minute)

1. Rhombus diagonal properties

   The diagonals of a rhombus meet at 90°, creating four congruent right-angled triangles; this enables applying Pythagoras' theorem to find side length from diagonals.

2. Rectangle diagonals vs Rhombus diagonals

   Rectangle diagonals are EQUAL but not perpendicular; rhombus diagonals are PERPENDICULAR but not equal in length.

3. Proving a figure is a square

   First prove it is a rectangle, then prove adjacent sides are equal (or diagonals are perpendicular).

Practise Parallelograms II questions today

Source: NIE G.C.E. (O/L) Mathematics Syllabus (Grade 10, Unit 16)

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Grade 10 · Term 2