Similar Triangles

Definition

Similar triangles are triangles that have the same shape but different sizes. They have corresponding angles that are congruent and corresponding sides that are proportional to each other.

5 Must Know Facts For Your Next Test

1. The ratio of corresponding side lengths between similar triangles is constant and known as the scale factor.
2. Similar triangles have the same angle measures, even though the side lengths may differ.
3. Corresponding angles in similar triangles are congruent, meaning they are equal in measure.
4. The proportion of side lengths in similar triangles can be used to solve for unknown side lengths.
5. Similar triangles are often used in right triangle trigonometry to solve for missing sides or angles.

Review Questions

• Explain how the concept of similar triangles is applied in right triangle trigonometry.
  • In right triangle trigonometry, similar triangles are used to establish the relationships between the sides and angles of a right triangle. By recognizing that right triangles with the same angle measures are similar, we can use the proportional side lengths to determine unknown side lengths or angles. This is the foundation of trigonometric ratios, such as sine, cosine, and tangent, which rely on the properties of similar right triangles.
• Describe the role of the scale factor in the relationship between similar triangles.
  • The scale factor is the constant ratio of corresponding side lengths between two similar triangles. It represents the factor by which one triangle is scaled up or down to create the other similar triangle. The scale factor allows you to determine the lengths of unknown sides in one triangle based on the known side lengths of the other similar triangle. Understanding the scale factor is crucial for solving problems involving similar triangles, as it enables the use of proportional reasoning to find missing measurements.
• Analyze how the congruence of angles and the proportionality of sides in similar triangles are used to solve for unknown values.
  • The defining characteristics of similar triangles - congruent angles and proportional sides - are the key to solving for unknown values. Since the angles are congruent, we can use the known angle measures to set up proportions between the corresponding side lengths of the similar triangles. By using the constant scale factor, we can then solve for the missing side lengths or angles. This powerful property of similar triangles allows us to use the known information in one triangle to determine the unknown values in the other, which is essential in right triangle trigonometry and a variety of other mathematical applications.

Related terms

Congruent Angles: Angles that are equal in measure, typically denoted by the same angle symbol.

Proportional Sides: Sides of triangles that have the same ratio of lengths, maintaining the same shape.

Scale Factor: The ratio of corresponding side lengths between two similar triangles, which is constant.