is the area between the function and the x-axis where ranges from to . According to the Fundamental theorem of calculus, if the definite integral can be calculated by: To take the definite integral of this function, one would find the antiderivative of the function at and subtract the value of from this. This will be equal to the area under the function in . A definite integral can be thought of as a Riemann sum of infinitely small rectangles, or