# Geometry: Triangles 165

This class describes the properties of the various types of triangles and demonstrates how they are used to solve sample part drawings.

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## Class Details

Class Name:
Geometry: Triangles 165
Description:
This class describes the properties of the various types of triangles and demonstrates how they are used to solve sample part drawings.
Version:
1.0
Difficulty:
Beginner
Number of Lessons:
16
Spanish, Chinese
Related 2.0 Class:
Geometry: Triangles 161

## Class Outline

• Objectives
• What Is a Triangle?
• Measurements of Interior Angles
• Sum of Interior Angles: Sample Problem
• Sum of Interior Angles: Solution
• Constructing a Triangle: Sample Problem
• Types of Triangles by Sides
• Types of Triangles by Angles
• Isosceles and Equilateral Triangles
• Relationship Between Sides and Angles
• Calculating Area of a Triangle
• Right Triangles
• Right Triangle: Sample Problem
• Two Right Triangles: First Solution
• Two Right Triangles: Second Solution
• Summary

## Objectives

• Define triangle.
• Describe how the angles of a triangle relate to each other.
• Distinguish between essential and nonessential information for solving a problem using triangle geometry.
• Solve a geometric problem using the interior angles of a triangle.
• Solve a geometric problem by adding a triangle to a drawing.
• Match triangles according to their sides.
• Match triangles according to their angles.
• Describe the characteristics of an isosceles triangle.
• Describe the characteristics of an equilateral triangle.
• Describe the relationship between the sides and angles of a triangle.
• Solve for the area of a triangle.
• Describe the characteristics of a right triangle.
• Solve a geometric problem using a right triangle.
• Identify right angles in a typical shop print.

## Certifications

SME
• CMfgT
MSSC
• MSSC Quality Practices and Measurement

## Glossary

Vocabulary Term Definition
acute triangle A triangle containing three angles that are all less than 90 degrees.
adjacent angles Two angles that share the same vertex and one side. The two sides that are not shared form a larger angle.
altitude In a triangle, a line drawn perpendicular to the base, from the base to the opposite vertex, that represents the height of the triangle.
angle A shape formed by two rays or line segments sharing a common endpoint or two lines that intersect. An angle has one vertex and two sides.
area The size of the space contained within an enclosed two-dimensional figure. Area is typically measured in square units such as square inches or square centimeters.
base In an isosceles triangle, the one side that is not equal to the other sides.
base angle In an isosceles triangle, one of the two angles formed by the base and a leg.
congruent Equal or similar to each other.
equilateral triangle A triangle containing three equal sides that are the same length.
interior angle An angle located within a closed figure. A triangle has three interior angles.
isosceles triangle A triangle containing two equal sides that are the same length.
leg In an isosceles triangle, one of the two sides that are equal in length.
obtuse triangle A triangle containing one angle that is greater than 90 degrees. The other two angles must total less than 90 degrees.
perpendicular Forming a 90° right angle.
perpendicular lines Two lines that intersect to form a 90° angle.
right angle An angle that measures exactly 90 degrees.
right triangle A triangle containing exactly one 90° angle. The other two angles must total exactly 90 degrees.
scalene triangle A triangle containing three unequal sides that are all different lengths.
supplementary angle Two angles that, when added together, equal 180 degrees.
triangle A closed figure with exactly three sides. The three sides meet to form three interior angles.
vertex A point where two lines or line segments meet or intersect. A triangle has three vertices.
vertex angle In an isosceles triangle, the angle formed by the two legs of equal length. The vertex angle is always opposite the base.
vertical angles Two angles that share the same vertex and are positioned directly opposite one another. Vertical angles are formed whenever two lines intersect.
vertices The plural term for vertex.