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## 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 45°-45°-90° triangle has the proportions 1:1:√2. All the lengths of these sides can be easily found if we only know the length...

## 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 the other hand, congruent triangles have corresponding sides with the same measurements. This means that congruent triangles...

## 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 of two of the sides of the triangle is greater than the third side of the triangle. If we have a segment that is greater than the sum of the other two...

## 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, but not equal sides. The proportions of the corresponding sides of similar figures is called the scale factor and can be used to describe how big...

## 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 we can divide any polygon into triangles. If the polygon is regular, we can calculate the measure of one of its interior angles by dividing the total...