Angles of a Triangle: Triangles in the Trees
This is one lesson in a larger Unit Plan that covers many properties of triangles and several other theorems. It has proofs, real world problems, constructions, a unit project, assessments, and more. In Lesson 9, “Triangles in the Trees (Angles of a Triangle)”, students investigate the Triangle Sum Theorem, Triangle Inequality Theorem, and Exterior Angle Theorem. One of the activities is a hands-on activity. Includes lesson plan, and a variety of downloadable student handouts (with and without Geometer's Sketchpad instructions). The entire unit plan can be found here. The Lesson investigates Triangle Sum Theorem with a hands-on activity. The Triangle Inequality Theorem is discovered through a drawing activity, as is Exterior Angle Theorem. There are also several real world connections.
- CLE 3108.4.1
- Develop the structures of geometry, such as lines, angles, planes, and planar figures, and explore their properties and relationships.
- CLE 3108.4.2
- Describe the properties of regular polygons, including comparative classification of them and special points and segments.
- GLE 0606.4.1
- Understand and use basic properties of triangles, quadrilaterals, and other polygons.
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- What properties of sides and angles of triangles are used in everyday situations?
- Why should we study Triangle Sum Theorem, Triangle Inequality Theorem and Exterior Angle Theorem for Triangles?
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