In the App enter formulas for the two boundary curves f and g, and values for the left and right limits a and b.[br][br]The total area between the two curves is given in purple.[br][br]Checking on the Right Riemann Sum checkbox shows a Right Riemann Sum approximation where the rectangles go from g(x) to f(x) at the right end of each subinterval. The height of these rectangles is [br]|f(x) - g(x)| for x at the right end of the subinterval. [br][br]The total area between the curves is [math]\int_a^b\mid f\left(x\right)-g\left(x\right)\mid dx[/math][br]If f(x) > g(x), then [br][math]\int_a^b\mid f\left(x\right)-g\left(x\right)\mid dx=\int_a^b\left(f\left(x\right)-g\left(x\right)\right)dx=\int_a^bf\left(x\right)dx-\int_a^bg\left(x\right)dx[/math][br]Using the checkboxes, you can see the integrals of f and g individually and the difference of these integrals.