Section 4.11

Approximate Methods for Evaluating Definite Integrals

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Problem 2531

Using the rectangle formula (n=12n=12), approximately compute

∫02πxsin⁡xdx \int _{0}^{2\pi }x\sin x dx

and compare the result with the exact value.

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Problem 2532

Use the trapezoid formula to compute the following integral and estimate its error:

∫01dx1+x(n=8). \int _{0}^{1}\dfrac {dx}{1+x}\quad (n=8) .
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Problem 2533

Use the trapezoid formula to compute the following integral and estimate its error:

∫01dx1+x3(n=12). \int _{0}^{1}\dfrac {dx}{1+x^{3}}\quad (n=12) .
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Problem 2534

Use the trapezoid formula to compute the following integral and estimate its error:

∫0π21−14sin⁡2xdx(n=6). \int _{0}^{\frac{\pi }{2}}\sqrt{1-\dfrac {1}{4}\sin ^{2}x} dx\quad (n=6) .
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Problem 2535

Use Simpson's formula to compute the following integral:

∫19xdx(n=4). \int _{1}^{9}\sqrt{x} dx\quad (n=4) .
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Problem 2536

Use Simpson's formula to compute the following integral:

∫0π3+cos⁡xdx(n=6). \int _{0}^{\pi }\sqrt{3+\cos x} dx\quad (n=6) .
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Problem 2537

Use Simpson's rule to compute the following integral:

∫0π2sin⁡xxdx(n=10). \int _{0}^{\frac{\pi }{2}}\dfrac {\sin x}{x} dx\quad (n=10) .
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Problem 2538

Use Simpson's rule to compute the following integral:

∫01xdxln⁡(1+x)(n=6). \int _{0}^{1}\dfrac {x dx}{\ln (1+x)}\quad (n=6) .
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Problem 2539

Taking n=10n=10, compute the Gauss constant (Catalan constant)

C=∫01arctan⁡xxdx. C=\int _{0}^{1}\dfrac {\arctan x}{x} dx .
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Problem 2540

Use the formula

π4=∫01dx1+x2 \dfrac {\pi }{4}=\int _{0}^{1}\dfrac {dx}{1+x^{2}}

to compute the number π\pi accurate to 10−510^{-5}.

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Problem 2541

Compute

∫01ex2dx \int _{0}^{1}e^{x^{2}} dx

accurate to 0.0010.001.

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Problem 2542

Compute

∫01(ex−1)ln⁡1xdx \int _{0}^{1}(e^{x}-1)\ln \dfrac {1}{x} dx

accurate to 10−410^{-4}.

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Problem 2543

Approximately compute the probability integral

∫0+∞e−x2dx. \int _{0}^{+\infty }e^{-x^{2}} dx .
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Problem 2544

Approximately find the perimeter of an ellipse with semi-axes a=10a=10 and b=6b=6.

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Problem 2545

Taking Δx=π3\Delta x=\dfrac {\pi }{3}, plot pointwise the graph of the function

y=∫0xsin⁡ttdt(0⩽x⩽2π) y=\int _{0}^{x}\dfrac {\sin t}{t} dt\quad (0\leqslant x\leqslant 2\pi )
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