Learning goals: Teacher Facing Generalize a process for finding the area of a circle, and justify (orally) why this can be abstracted as $\pi r^2$. Show how a circle can be decomposed and rearranged to approximate a polygon, and justify (orally and in writing) that the area of this polygon is equal to half of the circle’s circumference multiplied by its radius. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from 7.3 Measuring Circles, Grade 7.