# Lesson 5

What is an Angle?

### Lesson Purpose

### Lesson Narrative

In this lesson, students are introduced to angles. They learn that an angle can be defined in terms of the geometric parts they have been working with in this unit.

In previous grades, students have used “square corners” to describe right angles within two-dimensional shapes. They may have considered an angle as the space within a square corner or the “pointy” corner itself. Here, students learn that an **angle** is a geometric figure made up of two rays that share the same endpoint, which we refer to as the **vertex** of the angle.

Throughout the lesson, students use the vocabulary they have developed to describe other geometric figures to identify and describe angles. Monitor for the ways students reason about how to describe the size of angles. Students will compare and measure angles in future lessons.

- Engagement

### Learning Goals

Teacher Facing

- Identify angles in two-dimensional figures.
- Recognize angles as geometric figures that are formed wherever two rays share a common endpoint.

### Student Facing

- Let’s look for angles and find out ways to describe them.

### Required Materials

### Required Preparation

Activity 1:

- Create a set of cards (4 cards total) for each group of 2 from the blackline master.
- Each group of 2 needs 2 cards (sets 1 and 2). Additional cards (sets 3A and 3B) can be used for extension.

### Lesson Timeline

Warm-up | 5 min |

Activity 1 | 15 min |

Activity 2 | 15 min |

Activity 3 | 10 min |

Lesson Synthesis | 10 min |

Cool-down | 5 min |

### Teacher Reflection Questions

### Suggested Centers

- Target Measurements (2–5), Stage 4: Degrees (Addressing)
- Compare (1–5), Stage 5: Fractions (Supporting)

### Print Formatted Materials

Teachers with a valid work email address can click here to register or sign in for free access to Cool Down, Teacher Guide, and PowerPoint materials.

Student Task Statements | docx | |

Lesson Cover Page | docx | |

Cool Down | Log In | |

Teacher Guide | Log In | |

Teacher Presentation Materials | docx | |

Blackline Masters | zip |