Browse all lessons by topic (each link opens the full lesson page).
Area & Volume
- Length, Area, and Volume: What’s the Difference?
- Why the Area of a Circle is \(\pi r^2\) (Visual Explanation)
Pythagorean Theorem (Visual Proofs)
- Pythagorean Formula
- Pythagoras Theorem (\(a^2 + b^2 = c^2\)) – Visual Proof 1
- Pythagoras Theorem (\(a^2 + b^2 = c^2\)) – Visual Proof 2
- Pythagoras Theorem (Example)
Triangles
- Types of Triangles
- Triangles (Basics)
- Sum of Angles of a Triangle is 180° (Proof)
- Find the Missing Angle of a Triangle
- Sum of Exterior Angles of a Triangle (Proof)
- Exterior Angle Theorem of a Triangle
- Two Exterior Angles at a Vertex are Equal (Proof)
- Two Exterior Angles are Equal at a Vertex (Quick Proof)
Polygons
Introduction
Circle
Algebra
- \((a – b)^2\) – Geometric Derivation
- \((a + b)^2\) – Geometric Derivation
- \(a^2 – b^2\) – Geometric Derivation
- \(a^2 – b^2\) – Algebraic Proof