In the previous module, we discussed the difference between a
definite integral, e.g. ∫baf(x)dx, an
integral function, e.g. ∫xaf(t)dt. We now introduce notation for an antiderivative, called an
indefinite integral, e.g.
∫f(x)dx. In other words, If
F′(x)=f(x), we say F(x)=∫f(x)dx.
By the Fundamental Theorem of Calculus
I, since F′(x)=ddx∫xaf(t)dt=f(x), we have ∫f(x)dx=F(x)=∫xaf(t)dt.
This shows that the integral function is indeed an
antiderivative; it is the antiderivative of its integrand.
All antiderivatives are the same, up to adding a constant, and
indeed changing the value of a in F(x)=∫xaf(t)dt
changes F(x) by a constant, so both antiderivatives and integral
functions are only defined up to a constant.
Don't get too bogged down in the previous two paragraphs, but
you do need to understand the three types of "integrals" listed
above. From now on, the notation ∫f(x)dx will refer
to the antiderivative, and we'll usually just call it "the
antiderivative of f(x)" or "the integral of f(x)" (with
respect to x) for short.
∫f(x)dx is the antiderivative
of f.
Notice the difference between a definite integral and an indefinite
integral. With our new notation, the Fundamental
Theorem of Calculus II says that ∫baf(x)dx=∫f(x)dx|ba
This video gives the basic techniques for finding antiderivatives.