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# Introduction to integration

### Fundamental Theorem of Calculus

The Fundamental Theorem of Calculus states:
$\int^b_af(x) \; \mathrm{d} x = F(b) - F(a)$ where  $$F(x)$$ is the antiderivative of $$f(x)$$.

There are two types of integrals:

• Indefinite integral: No limits involved, produces an algebraic formula with an unknown constant.  The indefinite integral has the notation, and terminology:

$\underbrace{\int \overbrace{f(x)}^{\mbox{integrand}} \; \mathrm{d} x}_{\mbox{integral}} = F(x) + \underbrace{C}_{\mbox{constant of integration}}$

• Definite integral: Always evaluated between limits to produce a measurable quantity.  This is the same as the net area under the curve between the limits.

For example find the indefinite integrals:

1. $$\displaystyle \int\frac{2x^3 + 3x + 1}{x} \; \mathrm{d} x$$
2. $$\displaystyle \int (\cos x - e^x) \; \mathrm{d} x$$
3. $$\displaystyle \int \sqrt{x^3} + x^{\frac{2}{3}} \; \mathrm{d} x$$