How to use
Enter the function f(x) in the text input field marked "f(x)=".

 Example: f (x)=4-x2

Click the "Graph" button (this button also refreshes the graph).

Enter the endpoints of the interval [a,b] for the definite integral in the text input fields marked "a=" and "b=", and click the "Graph" button to refresh.

 Example: [a,b]=[-2,2]

Click the "+" and "-" buttons under the labels marked "n=" to change the number of subintervals used for each method.

 Example: n=20 for both

To erase the graph and all input fields, setting the "n=" fields to default values, click the "Clear" button.

 Polynomial: f (x)=4-x2, [a,b]=[-2,2],
n=20 for both

 Exponential: f (x)=e2, [a,b]=[0,2],
n=10 for both

 Trigonometric: f (x) = sin x, [a,b]=[0,3.14159],
n=10 for both

Other Notes
The area under the curve on the interval [a,b] is shaded so that positive areas are blue and negative areas are red. The approximate area computed by each method is shown in the labels marked "Area=".