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# 4: The Definite Integral

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• 4.1: Determining Distance Traveled from Velocity
f we know the velocity of a moving body at every point in a given interval and the velocity is positive throughout, we can estimate the object’s distance traveled and in some circumstances determine this value exactly. In particular, when velocity is positive on an interval, we can find the total distance traveled by finding the area under the velocity curve and above the t-axis on the given time interval. We may only be able to estimate this area, depending on the shape of the velocity curve.
• 4.2: Riemann Sums
A Riemann sum is simply a sum of products of the form $$f (x^∗_i )\Delta x$$ that estimates the area between a positive function and the horizontal axis over a given interval. If the function is sometimes negative on the interval, the Riemann sum estimates the difference between the areas that lie above the horizontal axis and those that lie below the axis.
• 4.3: The Definite Integral
The Riemann sum of a continuous function provides an estimate of the net signed area bounded by the function and the horizontal axis on the interval. Increasing the number of subintervals in the Riemann sum improves the accuracy of this estimate, and letting the number of subintervals increase without bound results in the values of the corresponding Riemann sums approaching the exact value of the enclosed net signed area.
• 4.4: The Fundamental Theorem of Calculus
We can find the exact value of a definite integral without taking the limit of a Riemann sum or using a familiar area formula by finding the antiderivative of the integrand, and hence applying the Fundamental Theorem of Calculus.
• 4.E: The Definite Integral (Exercises)
These are homework exercises to accompany Chapter 4 of Boelkins et al. "Active Calculus" Textmap.