This important theorem says that if f is the derivative of F then the definite
integral of f gives the net change in F as x varies from a to b. It also says that we
can evaluate any definite integral for which we can find an antiderivative of a
continuous function.
By extension, a definite integral can be evaluated for any function that is
bounded and piecewise continuous. Such functions are said to be integrable.
B. PROPERTIES OF DEFINITE INTEGRALS
The following theorems about definite integrals are important.
Fundamental Theorem of Calculus
THE FUNDAMENTAL THEOREM OF CALCULUS:
If f and g are both integrable functions of x on [a,b], then
Mean Value Theorem for Integrals
THE MEAN VALUE THEOREM FOR INTEGRALS: If f is continuous on [a,b] there
exists at least one number c, a < c < b, such that
By the comparison property, if f and g are integrable on [a,b] and if f(x) ≤
g(x) for all x in [a,b], then
The evaluation of a definite integral is illustrated in the following examples. A
calculator will be helpful for some numerical calculations.