Common Core Geometry Module 4 Lesson 9 Example 1 Pg. 113

This follows Module 4 Lesson 9 Example 1, finding the area of a triangle by decomposition. Complete the rectangle around a given triangle, then compute the area of that rectangle and subtract off the three exterior right triangles to be left with the area of the original triangle. As an extension, you can move the triangle away from the origin. Points are "snapped to grid" for convenience.