微积分I(标准路径) · free preview

§6.5 Improper integrals (continued)

什么是反常积分?为什么它们很重要?

1. Improper Integrals Involving Unbounded Integrands

Improper Integrals Involving Unbounded Integrands

2. Summary

Summary

3. An integrable singularity at the origin

The integral ∫011x1/3 dx\int_0^1\frac{1}{x^{1/3}}\,dx has a vertical asymptote at x=0x=0, yet it converges because

4. A divergence hidden in the middle

The integral ∫−221x2 dx\int_{-2}^2\frac{1}{x^2}\,dx diverges because

5. Tangent blowing up inside a window

The integral ∫0π/2tan⁡(x) dx\int_0^{\pi/2}\tan(x)\,dx diverges because

6. A square root singularity tamed

Using the antiderivative −24−x-2\sqrt{4-x}, evaluate ∫1414−x dx\int_1^4\frac{1}{\sqrt{4-x}}\,dx. The exact value is 232\sqrt{3}. Report the decimal, rounded to three places.

7. An arcsine endpoint

Using the antiderivative arcsin⁡(x)\arcsin(x), evaluate ∫0111−x2 dx\int_0^1\frac{1}{\sqrt{1-x^2}}\,dx. The exact value is π2\frac{\pi}{2}. Report the decimal, rounded to three places.

8. Not every finite bound integral is improper

The integral ∫02e−x dx\int_0^2e^{-x}\,dx is a proper integral with value 1−e−21-e^{-2}, since the integrand is continuous on all of [0,2][0,2].

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