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Lesson 4-1: Angle Relationships & Properties

Scenario: Architecture Design - Learn about angle relationships through building and design projects!

Duration: 55-70 minutesScenario: Architecture Design

Learning Objectives

  • Identify and classify different types of angles
  • Understand complementary and supplementary angles
  • Work with vertical angles and their properties
  • Apply angle relationships to architectural problems

Architecture Design Scenario

The Problem

You're designing a modern building with intersecting walls. The architect needs to know the angles where walls meet to ensure proper structural support and aesthetic appeal.

Design Challenge:
Two walls intersect at a point. One angle formed is 65°. Find all other angles at this intersection.

Visual Representation

65°
?
?
?

Intersecting walls create four angles at the intersection point

Types of Angles

Basic Angle Classifications

By Size

  • • Acute: 0° < angle < 90°
  • • Right: angle = 90°
  • • Obtuse: 90° < angle < 180°
  • • Straight: angle = 180°

By Position

  • • Adjacent: Share a common side
  • • Vertical: Opposite each other
  • • Complementary: Sum to 90°
  • • Supplementary: Sum to 180°

Vertical Angles

The Rule

Vertical Angles Theorem: Vertical angles are always equal.

When two lines intersect, the angles opposite each other are called vertical angles and they have the same measure.

Solving the Architecture Problem

Given: One angle is 65°

Step 1: Find the vertical angle

Vertical angles are equal, so the opposite angle is also 65°

Step 2: Find the supplementary angles

180° - 65° = 115°

Answer: The four angles are 65°, 65°, 115°, and 115°

Complementary and Supplementary Angles

Definitions

Complementary Angles

Two angles that add up to 90°

Example: 30° + 60° = 90°

Supplementary Angles

Two angles that add up to 180°

Example: 120° + 60° = 180°

Practice Example

In a building design, two support beams meet at a 45° angle. Find the complementary and supplementary angles.

Complementary angle: 90° - 45° = 45°

Supplementary angle: 180° - 45° = 135°

Practice Problems

Problem 1: Vertical Angles

Two lines intersect. One angle is 72°. Find all four angles formed.

Your solution:

Problem 2: Complementary Angles

Two complementary angles are in the ratio 2:3. Find the measure of each angle.

Your calculation: