AP Calculus BC Flashcards: Evaluating Improper Integrals

Study Evaluating Improper Integrals in AP Calculus BC with focused flashcards that help you recognize the idea, recall the key rule, and apply it in practice-style prompts.

AP Calculus BC

Evaluating Improper Integrals

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Determine convergence: 0ex2dx\int_{0}^{\infty} e^{-x^2} \, dx.

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ANSWER

Converges. Gaussian integral converges due to exponential decay.

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This deck focuses on Evaluating Improper Integrals, giving you a quick way to review the definitions, rules, and examples that matter most for AP Calculus BC.

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Flashcard 1: Determine convergence: 0ex2dx\int_{0}^{\infty} e^{-x^2} \, dx.

Answer: Converges. Gaussian integral converges due to exponential decay.

Flashcard 2: When does an integral abf(x)dx\textstyle \int_{a}^{b} f(x) \, dx become improper?

Answer: If aa, bb, or f(x)f(x) are infinite or unbounded. Any infinite bound or unbounded integrand makes it improper.

Flashcard 3: What is an improper integral?

Answer: An integral with infinite limits or an unbounded integrand. Defined when limits of integration or integrand are infinite.

Flashcard 4: Evaluate: \textstyle \text{∫}_{0}^{1} \frac{1}{\text{√}x} \text{dx}.

Answer: Converges to 22. lima0+[2x]a1=210=2\lim_{a \to 0^+} [2\sqrt{x}]_a^1 = 2\sqrt{1} - 0 = 2.

Flashcard 5: What does it mean if an improper integral converges?

Answer: The limit defining the integral exists and is finite. The limit exists and equals a finite real number.

Flashcard 6: Identify convergence: 11xdx\int_{1}^{\infty} \frac{1}{\sqrt{x}} \, dx.

Answer: Diverges. Since p=121p = \frac{1}{2} \leq 1, the integral diverges.

Flashcard 7: What does it mean if an improper integral converges?

Answer: The limit defining the integral exists and is finite. The limit exists and equals a finite real number.

Flashcard 8: Identify the singularity: 011xdx\textstyle \int_{0}^{1} \frac{1}{x} dx.

Answer: Unbounded integrand at x=0x = 0. Integrand has vertical asymptote at the lower limit.

Flashcard 9: Determine behavior: \textstyle \text{∫}_{0}^{1} \frac{1}{\text{√}x} \text{dx}

Answer: Converges. Power 12>1-\frac{1}{2} > -1 ensures convergence at x=0x = 0.

Flashcard 10: Evaluate: \textstyle \text{∫}_{0}^{\text{∞}} e^{-x} \text{dx}.

Answer: Converges to 11. limb[ex]0b=0(1)=1\lim_{b \to \infty} [-e^{-x}]_0^b = 0 - (-1) = 1.

Flashcard 11: Convert to limit form: 0exdx\textstyle ∫_{-∞}^{0} e^{x} \, dx.

Answer: limaa0exdx\textstyle \lim_{a \to -∞} ∫_{a}^{0} e^{x} \, dx. Negative infinite lower limit requires limit form.

Flashcard 12: Convert to limit: \textstyle \text{∫}_{0}^{1} \frac{1}{x} \text{dx}.

Answer: \textstyle \text{lim}_{a \to 0^+} \text{∫}_{a}^{1} \frac{1}{x} \text{dx}. Integrand 1x\frac{1}{x} is unbounded at lower limit x=0x = 0.

Flashcard 13: Identify singularity: 11(x1)2dx\int_{1}^{\infty} \frac{1}{(x-1)^2} dx.

Answer: Unbounded integrand at x=1x=1. Function becomes infinite at the lower limit x=1x = 1.

Flashcard 14: Evaluate: 1exdx\textstyle \int_{1}^{\infty} e^{-x} \text{dx}

Answer: Converges to 1e\frac{1}{e}. limb[ex]1b=0(e1)=1e\lim_{b \to \infty} [-e^{-x}]_1^b = 0 - (-e^{-1}) = \frac{1}{e}

Flashcard 15: Evaluate: 0111x2dx\int_{0}^{1} \frac{1}{\sqrt{1-x^2}} \, dx.

Answer: Converges to π2\frac{\pi}{2}. Arcsine function evaluation: arcsin(1)arcsin(0)=π2\arcsin(1) - \arcsin(0) = \frac{\pi}{2}.

Flashcard 16: State the condition for the convergence of 0a(ax)1/2dx\int_{0}^{a} (a-x)^{-1/2} \, dx.

Answer: Converges if a>0a > 0. For a>0a > 0, the singularity at x=ax = a is integrable.

Flashcard 17: Evaluate: 11x(lnx)2dx\textstyle \int_{1}^{\infty} \frac{1}{x (\ln x)^2} \, dx.

Answer: Converges. Higher power in denominator ensures convergence.

Flashcard 18: What is convergence for \textstyle \text{∫}_{1}^{\text{∞}} \frac{1}{x^4} \text{dx}?

Answer: Converges to 13\frac{1}{3}. limb[13x3]1b=0(13)=13\lim_{b \to \infty} [-\frac{1}{3x^3}]_1^b = 0 - (-\frac{1}{3}) = \frac{1}{3}.

Flashcard 19: What is an improper integral?

Answer: An integral with infinite limits or an unbounded integrand. Defined when limits of integration or integrand are infinite.

Flashcard 20: What is convergence for 11x4dx\int_1^\infty \frac{1}{x^4} \, dx?

Answer: Converges to 13\frac{1}{3}. limb[13x3]1b=0(13)=13\lim_{b \to \infty} [-\frac{1}{3x^3}]_1^b = 0 - (-\frac{1}{3}) = \frac{1}{3}.

Flashcard 21: Evaluate limit: lima0+a11xdx\textstyle \lim_{a \to 0^+} \int_{a}^{1} \frac{1}{x} dx.

Answer: Diverges. lima0+[lnx]a1=0()=\lim_{a \to 0^+} [\ln x]_a^1 = 0 - (-\infty) = \infty.

Flashcard 22: Determine behavior: 011xpdx\textstyle \int_{0}^{1} \frac{1}{x^p} \text{dx} for p<1p<1.

Answer: Converges. When p<1p < 1, the singularity at x=0x = 0 is integrable.

Flashcard 23: Find the limit: limb1b1x3dx\textstyle \lim_{b \to \infty} \int_{1}^{b} \frac{1}{x^3} dx.

Answer: Converges to 12\frac{1}{2}. limb[12x2]1b=0(12)=12\lim_{b \to \infty} [-\frac{1}{2x^2}]_1^b = 0 - (-\frac{1}{2}) = \frac{1}{2}.

Flashcard 24: Evaluate: 1exdx\int_{1}^{\infty} e^{-x} \, dx.

Answer: Converges to 1e\frac{1}{e}. limb[ex]1b=0(e1)=1e\lim_{b \to \infty} [-e^{-x}]_1^b = 0 - (-e^{-1}) = \frac{1}{e}

Flashcard 25: Evaluate: \textstyle \text{∫}_{0}^{\text{∞}} e^{-x} \text{dx}.

Answer: Converges to 11. limb[ex]0b=0(1)=1\lim_{b \to \infty} [-e^{-x}]_0^b = 0 - (-1) = 1.

Flashcard 26: Find the limit: limb1b1x3dx\textstyle \lim_{b \to \infty} \int_{1}^{b} \frac{1}{x^3} \text{dx}

Answer: Converges to 12\frac{1}{2}. limb[12x2]1b=0(12)=12\lim_{b \to \infty} [-\frac{1}{2x^2}]_1^b = 0 - (-\frac{1}{2}) = \frac{1}{2}

Flashcard 27: Convert to limit: 0xexdx\textstyle \int_{0}^{\infty} x e^{-x} \, dx.

Answer: limb0bxexdx\textstyle \lim_{b \to \infty} \int_{0}^{b} x e^{-x} \, dx. Infinite upper limit requires limit evaluation.

Flashcard 28: Evaluate: 11x2dx\int_{1}^{\infty} \frac{1}{x^2} dx

Answer: Converges to 11. limb[1x]1b=limb(0+1)=1\lim_{b \to \infty} [-\frac{1}{x}]_1^b = \lim_{b \to \infty} (0 + 1) = 1

Flashcard 29: 0xexdx\textstyle \int_{0}^{\infty} x e^{-x} \, dx

Answer: limb0bxexdx\textstyle \lim_{b \to \infty} \int_{0}^{b} x e^{-x} \, dx. Infinite upper limit requires limit evaluation.

Flashcard 30: Determine convergence: 0ex2dx\textstyle \int_{0}^{\infty} e^{-x^2} \text{dx}

Answer: Converges. Gaussian integral converges due to exponential decay.

Flashcard 31: What is the behavior of \textstyle \text{∫}_{0}^{1} x^{-1/3} \text{dx}?

Answer: Converges. Power 13>1-\frac{1}{3} > -1 ensures convergence.

Flashcard 32: Identify the type of improper integral: 011xdx\int_{0}^{1} \frac{1}{\sqrt{x}} \text{dx}.

Answer: Unbounded integrand at x=0x = 0. 1x\frac{1}{\sqrt{x}} becomes infinite as x0+.x \to 0^+.

Flashcard 33: State the behavior of 01x1dx\int_{0}^{1} x^{-1} dx.

Answer: Diverges. Same as 011xdx\int_0^1 \frac{1}{x} dx which diverges.

Flashcard 34: Identify singularity: 11(x1)2dx\textstyle \int_{1}^{\infty} \frac{1}{(x-1)^2} \text{d}x.

Answer: Unbounded integrand at x=1x=1. Function becomes infinite at the lower limit x=1x = 1.

Flashcard 35: Determine behavior: 011xdx\int_{0}^{1} \frac{1}{\sqrt{x}} \mathrm{d}x.

Answer: Converges. Power 12>1-\frac{1}{2} > -1 ensures convergence at x=0x = 0.

Flashcard 36: Evaluate: 11x(lnx)2dx\textstyle \int_{1}^{\infty} \frac{1}{x (\ln x)^2} \, dx.

Answer: Converges. Higher power in denominator ensures convergence.

Flashcard 37: What is the behavior of ex2dx\int_{-\infty}^{\infty} e^{-x^2} \, dx?

Answer: Converges to π\sqrt{\pi}. Famous Gaussian integral equals π\sqrt{\pi}.

Flashcard 38: Identify convergence: 11xdx\int_{1}^{\infty} \frac{1}{\sqrt{x}} dx.

Answer: Diverges. Since p=121p = \frac{1}{2} \leq 1, the integral diverges.

Flashcard 39: Convert to limit form: 0exdx\int_{-\infty}^{0} e^{x} \, dx.

Answer: limaa0exdx\lim_{a \to -\infty} \int_{a}^{0} e^{x} \, dx. Negative infinite lower limit requires limit form.

Flashcard 40: What is the behavior of ex2dx\int_{-\infty}^{\infty} e^{-x^2} \, dx?

Answer: Converges to π\sqrt{\pi}. Famous Gaussian integral equals π\sqrt{\pi}.

Flashcard 41: When does an integral abf(x)dx\int_{a}^{b} f(x) \, dx become improper?

Answer: If aa, bb, or f(x)f(x) are infinite or unbounded. Any infinite bound or unbounded integrand makes it improper.

Flashcard 42: What is the behavior of \textstyle \text{∫}_{0}^{1} x^{-1/3} \text{dx}?

Answer: Converges. Power 13>1-\frac{1}{3} > -1 ensures convergence.

Flashcard 43: Evaluate limit: lima0+a11xdx\textstyle \lim_{a \to 0^+} \int_{a}^{1} \frac{1}{x} \text{dx}

Answer: Diverges. lima0+[lnx]a1=0()=\lim_{a \to 0^+} [\ln x]_a^1 = 0 - (-\infty) = \infty

Flashcard 44: Identify the singularity: 011xdx\textstyle \int_{0}^{1} \frac{1}{x} \, dx.

Answer: Unbounded integrand at x=0x = 0. Integrand has vertical asymptote at the lower limit.

Flashcard 45: What is the behavior of 0exdx\int_{-\infty}^{0} e^x \, dx?

Answer: Converges to 11. lima[ex]a0=10=1\lim_{a \to -\infty} [e^x]_a^0 = 1 - 0 = 1.

Flashcard 46: Explain divergence in the context of improper integrals.

Answer: The integral's limit is infinite or does not exist. The limit is infinite or undefined.

Flashcard 47: Explain divergence in the context of improper integrals.

Answer: The integral's limit is infinite or does not exist. The limit is infinite or undefined.

Flashcard 48: Convert to limit: 011xdx\int_{0}^{1} \frac{1}{x} \, \mathrm{d}x.

Answer: lima0+a11xdx\lim_{a \to 0^+} \int_{a}^{1} \frac{1}{x} \, \mathrm{d}x. Integrand 1x\frac{1}{x} is unbounded at lower limit x=0x = 0.

Flashcard 49: What is the behavior of \textstyle \text{∫}_{-\text{∞}}^{0} e^x \text{dx}?

Answer: Converges to 11. lima[ex]a0=10=1\lim_{a \to -\infty} [e^x]_a^0 = 1 - 0 = 1.

Flashcard 50: State the condition for the convergence of 0a(ax)1/2dx\textstyle \int_{0}^{a} (a-x)^{-1/2} \, dx.

Answer: Converges if a>0a > 0. For a>0a > 0, the singularity at x=ax = a is integrable.

Flashcard 51: Determine behavior: 011xpdx\textstyle \int_{0}^{1} \frac{1}{x^p} dx for p<1p<1.

Answer: Converges. When p<1p < 1, the singularity at x=0x = 0 is integrable.

Flashcard 52: Evaluate: \textstyle \text{∫}_{0}^{1} \frac{1}{\text{√}x} \text{dx}.

Answer: Converges to 22. lima0+[2x]a1=210=2\lim_{a \to 0^+} [2\sqrt{x}]_a^1 = 2\sqrt{1} - 0 = 2.

Flashcard 53: Evaluate: 0111x2dx\textstyle \int_{0}^{1} \frac{1}{\sqrt{1-x^2}} \, dx.

Answer: Converges to π2\frac{\pi}{2}. Arcsine function evaluation: arcsin(1)arcsin(0)=π2\arcsin(1) - \arcsin(0) = \frac{\pi}{2}.

Flashcard 54: Evaluate: \textstyle \text{∫}_{1}^{\text{∞}} \frac{1}{x^2} \text{dx}.

Answer: Converges to 11. limb[1x]1b=limb(0+1)=1\lim_{b \to \infty} [-\frac{1}{x}]_1^b = \lim_{b \to \infty} (0 + 1) = 1.

Flashcard 55: State the behavior of 01x1dx\int_0^1 x^{-1} \text{dx}

Answer: Diverges. Same as 011xdx\int_0^1 \frac{1}{x} dx which diverges.

Flashcard 56: Determine convergence: 11xdx\textstyle \int_{1}^{\infty} \frac{1}{x} \text{dx}.

Answer: Diverges. ln(x)\ln(x) grows without bound, so the integral diverges.