## Problems with Thales’ Theorem

Thales’ theorem is a special case of the inscribed angles theorem. This theorem says that if we have a triangle … Read more

## 3D Pythagorean Theorem – Formula and Examples

The 3D Pythagorean theorem is an extension of the 2D Pythagorean theorem that can be used to solve problems in … Read more

## Equilateral, Isosceles and Scalene Triangles

A triangle is a three-sided polygon that has three vertices and three interior angles. The sum of the interior angles … Read more

## Stellations – Diagrams and Examples

Stellations are formed when we extend the sides of a polygon and those sides intersect each other. The number of … Read more

## Missing Square Puzzle – Diagram and Solution

The missing square puzzle is an optical illusion found in mathematics that is used to teach reasoning using the axioms … Read more

## Special Triangles – Formulas and Examples

Special triangles are right triangles that have special proportions for their sides. The 30°-60°-90° triangle has the proportions 1:√3:2. The … Read more

## Similar and Congruent Triangles – Criteria

Similar triangles are characterized by having corresponding sides with the same proportions, but not necessarily with the same measurements. On … Read more

## Triangle Inequality – Definition, Proof and Examples

The triangular inequality is one of the most commonly known theorems in geometry. This theorem tells us that the sum … Read more

## Similar Figures and Scale Factors

Similar figures are characterized by always having the same shape, but not the same size. These figures have equal angles, … Read more

## Sum of Interior Angles of a Polygon – Formula and Examples

The sum of interior angles of any polygon can be calculated using a formula. The formula is derived considering that … Read more