In this activity, students will use the area formula involving the determinant of a matrix. For the area of a triangle, they will compare their answer found using the formula to the one found using the Area tool on the Graphs & Geometry screen.

Next, students will investigate the area of a convex polygon. They will divide the heptagon into triangles and then find the area of each triangle using the formula from the first problem. By summing all the areas of the triangles, students will have calculated the area of the heptagon.

Students will then find a formula for the area of any quadrilateral through trial and error on a Calculator page. By moving the vertices of the quadrilateral on the Graphs & Geometry screen, students can test several quadrilaterals easily.

Finally, students will find a formula for the area of a quadrilateral.