Section 1.4
Definite Integrals
Goals:
1 Express areas under a graph and antiderivatives using integral notation.
2 Derive antiderivatives from known derivatives.
3 Compute general antiderivatives.
4 Compute definite integrals using the Fundamental Theorem of Calculus.
5 Use u-substitution to compute integrals where necessary.
By definition, integrals compute area under a graph. The Fundamental Theorem of Calculus connects
integrals to antiderivatives, meaning that integrals can also be used to compute total change, given a
rate of change function.
Question 1.4.1
What Is an Antiderivative?
Definition
F (x) is antiderivative of a function f(x), if F
(x) = f(x).
Every derivative we know also tells us an antiderivative.
Example
d
dx
x
2
2
+ 5
= x so F (x) =
x
2
2
+ 5 is an antiderivative of f(x) = x.
Notice that
x
2
2
+ 2,
x
2
2
6, and
x
2
2
are also antiderivatives of f(x) = x.
Functions have infinitely many antiderivatives. Adding a constant to one antiderivative produces
another, since the derivative of a constant is 0. In fact, this is the only relationship between antideriva-
tives.
Theorem
If F (x) and G(x) are antideriavatives of f(x), then there is a constant c such that
F (x) = G(x) + c.
Since the antiderivatives are related this way, it is easy to express all of the antiderivatives of a
function at once.
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