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 starting point, which we refer to as the vertex of the angle.

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