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Section 5.1 Area and Estimating with Finite Sums

Example 5.1.1.

What is the area between the \(x\)-axis and the graph of \(f(x) =x^2+1\) between \(x=0\) and \(x=1\text{?}\)

Upper sum

\(\displaystyle \frac{1}{4}f(\frac{1}{4}) +\frac{1}{4}f(\frac{2}{4}) +\frac{1}{4}f(\frac{3}{4}) +\frac{1}{4}f(\frac{4}{4})\)

Lower sum

\(\displaystyle \frac{1}{4}f(\frac{0}{4}) +\frac{1}{4}f(\frac{1}{4}) +\frac{1}{4}f(\frac{2}{4}) +\frac{1}{4}f(\frac{3}{4})\)

Midpoint rule

\(\displaystyle \frac{1}{4}f(\frac{1}{8}) +\frac{1}{4}f(\frac{3}{8}) +\frac{1}{4}f(\frac{5}{8}) +\frac{1}{4}f(\frac{7}{8})\)

Common structure

\(\displaystyle \Delta x f(c_1) + \Delta x f(c_2) + \Delta x f(c_3) + \cdots + \Delta x f(c_n)\)