[Copy of] 6-1.11 Formula for the Area of a Triangle

This is an adaptation of OUR 6-1.9 Formula for the Area of a Triangle. This lesson aims to move the students to develop the shortcut for finding the area of a triangle by the standard formula. As students put this shortcut to work in future situations then this shortcut will solidify to the point where they are operating based on rules based on understanding-- hence they will become formal thinkers in terms of the area of a triangle where the base and height are known. Student Facing Goals I can use the area formula to find the area of any triangle. I can write and explain the formula for the area of a triangle. I know what the terms “base” and “height” refer to in a triangle. Lesson Narrative In this lesson students begin to reason about area of triangles more methodically: by generalizing their observations up to this point and expressing the area of a triangle in terms of its base and height. Students first learn about bases and heights in a triangle by studying examples and counterexamples. They then identify base-height measurements of triangles, use them to determine area, and look for a pattern in their reasoning to help them write a general formula for finding area (MP8). Students also have a chance to build an informal argument about why the formula works for any triangle (MP3).

By Patricia Stevens