All flashcards Flashcard 1: Evaluate: ∫ 1 ∞ e − x d x \int_{1}^{\infty} e^{-x} \, dx ∫ 1 ∞ e − x d x . Answer: Converges to 1 e \frac{1}{e} e 1 . lim b → ∞ [ − e − x ] 1 b = 0 − ( − e − 1 ) = 1 e \lim_{b \to \infty} [-e^{-x}]_1^b = 0 - (-e^{-1}) = \frac{1}{e} lim b → ∞ [ − e − x ] 1 b = 0 − ( − e − 1 ) = e 1
Flashcard 2: Find the limit: lim b → ∞ ∫ 1 b 1 x 3 d x \textstyle \lim_{b \to \infty} \int_{1}^{b} \frac{1}{x^3} dx lim b → ∞ ∫ 1 b x 3 1 d x . Answer: Converges to 1 2 \frac{1}{2} 2 1 . lim b → ∞ [ − 1 2 x 2 ] 1 b = 0 − ( − 1 2 ) = 1 2 \lim_{b \to \infty} [-\frac{1}{2x^2}]_1^b = 0 - (-\frac{1}{2}) = \frac{1}{2} lim b → ∞ [ − 2 x 2 1 ] 1 b = 0 − ( − 2 1 ) = 2 1 .
Flashcard 3: Evaluate limit: lim a → 0 + ∫ a 1 1 x d x \textstyle \lim_{a \to 0^+} \int_{a}^{1} \frac{1}{x} dx lim a → 0 + ∫ a 1 x 1 d x . Answer: Diverges. lim a → 0 + [ ln x ] a 1 = 0 − ( − ∞ ) = ∞ \lim_{a \to 0^+} [\ln x]_a^1 = 0 - (-\infty) = \infty lim a → 0 + [ ln x ] a 1 = 0 − ( − ∞ ) = ∞ .
Flashcard 4: Identify singularity: ∫ 1 ∞ 1 ( x − 1 ) 2 d x \int_{1}^{\infty} \frac{1}{(x-1)^2} dx ∫ 1 ∞ ( x − 1 ) 2 1 d x . Answer: Unbounded integrand at x = 1 x=1 x = 1 . Function becomes infinite at the lower limit x = 1 x = 1 x = 1 .
Flashcard 5: Evaluate: ∫ 0 1 1 1 − x 2 d x \textstyle \int_{0}^{1} \frac{1}{\sqrt{1-x^2}} \, dx ∫ 0 1 1 − x 2 1 d x . Answer: Converges to π 2 \frac{\pi}{2} 2 π . Arcsine function evaluation: arcsin ( 1 ) − arcsin ( 0 ) = π 2 \arcsin(1) - \arcsin(0) = \frac{\pi}{2} arcsin ( 1 ) − arcsin ( 0 ) = 2 π .
Flashcard 6: Identify the singularity: ∫ 0 1 1 x d x \textstyle \int_{0}^{1} \frac{1}{x} \, dx ∫ 0 1 x 1 d x . Answer: Unbounded integrand at x = 0 x = 0 x = 0 . Integrand has vertical asymptote at the lower limit.
Flashcard 7: Determine convergence: ∫ 0 ∞ e − x 2 dx \textstyle \int_{0}^{\infty} e^{-x^2} \text{dx} ∫ 0 ∞ e − x 2 dx Answer: Converges. Gaussian integral converges due to exponential decay.
Flashcard 8: Evaluate: ∫ 1 ∞ 1 x ( ln x ) 2 d x \textstyle \int_{1}^{\infty} \frac{1}{x (\ln x)^2} \, dx ∫ 1 ∞ x ( l n x ) 2 1 d x . Answer: Converges. Higher power in denominator ensures convergence.
Flashcard 9: Identify the type of improper integral: ∫ 0 1 1 x dx \int_{0}^{1} \frac{1}{\sqrt{x}} \text{dx} ∫ 0 1 x 1 dx . Answer: Unbounded integrand at x = 0 x = 0 x = 0 . 1 x \frac{1}{\sqrt{x}} x 1 becomes infinite as x → 0 + . x \to 0^+. x → 0 + .
Flashcard 10: Identify convergence: ∫ 1 ∞ 1 x d x \int_{1}^{\infty} \frac{1}{\sqrt{x}} \, dx ∫ 1 ∞ x 1 d x . Answer: Diverges. Since p = 1 2 ≤ 1 p = \frac{1}{2} \leq 1 p = 2 1 ≤ 1 , the integral diverges.
Flashcard 11: Convert to limit: ∫ 0 1 1 x d x \int_{0}^{1} \frac{1}{x} \, \mathrm{d}x ∫ 0 1 x 1 d x . Answer: lim a → 0 + ∫ a 1 1 x d x \lim_{a \to 0^+} \int_{a}^{1} \frac{1}{x} \, \mathrm{d}x lim a → 0 + ∫ a 1 x 1 d x . Integrand 1 x \frac{1}{x} x 1 is unbounded at lower limit x = 0 x = 0 x = 0 .
Flashcard 12: Determine convergence: ∫ 1 ∞ 1 x dx \textstyle \int_{1}^{\infty} \frac{1}{x} \text{dx} ∫ 1 ∞ x 1 dx . Answer: Diverges. ln ( x ) \ln(x) ln ( x ) grows without bound, so the integral diverges.
Flashcard 13: Determine behavior: ∫ 0 1 1 x d x \int_{0}^{1} \frac{1}{\sqrt{x}} \mathrm{d}x ∫ 0 1 x 1 d x . Answer: Converges. Power − 1 2 > − 1 -\frac{1}{2} > -1 − 2 1 > − 1 ensures convergence at x = 0 x = 0 x = 0 .
Flashcard 14: Convert to limit: ∫ 0 ∞ x e − x d x \textstyle \int_{0}^{\infty} x e^{-x} \, dx ∫ 0 ∞ x e − x d x . Answer: lim b → ∞ ∫ 0 b x e − x d x \textstyle \lim_{b \to \infty} \int_{0}^{b} x e^{-x} \, dx lim b → ∞ ∫ 0 b x e − x d x . Infinite upper limit requires limit evaluation.
Flashcard 15: State the condition for the convergence of ∫ 0 a ( a − x ) − 1 / 2 d x \textstyle \int_{0}^{a} (a-x)^{-1/2} \, dx ∫ 0 a ( a − x ) − 1/2 d x . Answer: Converges if a > 0 a > 0 a > 0 . For a > 0 a > 0 a > 0 , the singularity at x = a x = a x = a is integrable.
Flashcard 16: State the behavior of ∫ 0 1 x − 1 dx \int_0^1 x^{-1} \text{dx} ∫ 0 1 x − 1 dx Answer: Diverges. Same as ∫ 0 1 1 x d x \int_0^1 \frac{1}{x} dx ∫ 0 1 x 1 d x which diverges.
Flashcard 17: Evaluate: \textstyle \text{∫}_{0}^{1} \frac{1}{\text{√}x} \text{dx} . Answer: Converges to 2 2 2 . lim a → 0 + [ 2 x ] a 1 = 2 1 − 0 = 2 \lim_{a \to 0^+} [2\sqrt{x}]_a^1 = 2\sqrt{1} - 0 = 2 lim a → 0 + [ 2 x ] a 1 = 2 1 − 0 = 2 .
Flashcard 18: 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 19: 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 20: When does an integral ∫ a b f ( x ) d x \int_{a}^{b} f(x) \, dx ∫ a b f ( x ) d x become improper? Answer: If a a a , b b b , or f ( x ) f(x) f ( x ) are infinite or unbounded. Any infinite bound or unbounded integrand makes it improper.
Flashcard 21: What is the behavior of ∫ − ∞ ∞ e − x 2 d x \int_{-\infty}^{\infty} e^{-x^2} \, dx ∫ − ∞ ∞ e − x 2 d x ? Answer: Converges to π \sqrt{\pi} π . Famous Gaussian integral equals π \sqrt{\pi} π .
Flashcard 22: 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 23: Convert to limit form: ∫ − ∞ 0 e x d x \int_{-\infty}^{0} e^{x} \, dx ∫ − ∞ 0 e x d x . Answer: lim a → − ∞ ∫ a 0 e x d x \lim_{a \to -\infty} \int_{a}^{0} e^{x} \, dx lim a → − ∞ ∫ a 0 e x d x . Negative infinite lower limit requires limit form.
Flashcard 24: What is the behavior of \textstyle \text{∫}_{0}^{1} x^{-1/3} \text{dx} ? Answer: Converges. Power − 1 3 > − 1 -\frac{1}{3} > -1 − 3 1 > − 1 ensures convergence.
Flashcard 25: Evaluate: \textstyle \text{∫}_{0}^{\text{∞}} e^{-x} \text{dx} . Answer: Converges to 1 1 1 . lim b → ∞ [ − e − x ] 0 b = 0 − ( − 1 ) = 1 \lim_{b \to \infty} [-e^{-x}]_0^b = 0 - (-1) = 1 lim b → ∞ [ − e − x ] 0 b = 0 − ( − 1 ) = 1 .
Flashcard 26: What is convergence for ∫ 1 ∞ 1 x 4 d x \int_1^\infty \frac{1}{x^4} \, dx ∫ 1 ∞ x 4 1 d x ? Answer: Converges to 1 3 \frac{1}{3} 3 1 . lim b → ∞ [ − 1 3 x 3 ] 1 b = 0 − ( − 1 3 ) = 1 3 \lim_{b \to \infty} [-\frac{1}{3x^3}]_1^b = 0 - (-\frac{1}{3}) = \frac{1}{3} lim b → ∞ [ − 3 x 3 1 ] 1 b = 0 − ( − 3 1 ) = 3 1 .
Flashcard 27: What is the behavior of \textstyle \text{∫}_{-\text{∞}}^{0} e^x \text{dx} ? Answer: Converges to 1 1 1 . lim a → − ∞ [ e x ] a 0 = 1 − 0 = 1 \lim_{a \to -\infty} [e^x]_a^0 = 1 - 0 = 1 lim a → − ∞ [ e x ] a 0 = 1 − 0 = 1 .
Flashcard 28: Evaluate: \textstyle \text{∫}_{1}^{\text{∞}} \frac{1}{x^2} \text{dx} . Answer: Converges to 1 1 1 . lim b → ∞ [ − 1 x ] 1 b = lim b → ∞ ( 0 + 1 ) = 1 \lim_{b \to \infty} [-\frac{1}{x}]_1^b = \lim_{b \to \infty} (0 + 1) = 1 lim b → ∞ [ − x 1 ] 1 b = lim b → ∞ ( 0 + 1 ) = 1 .
Flashcard 29: Determine behavior: ∫ 0 1 1 x p d x \textstyle \int_{0}^{1} \frac{1}{x^p} dx ∫ 0 1 x p 1 d x for p < 1 p<1 p < 1 . Answer: Converges. When p < 1 p < 1 p < 1 , the singularity at x = 0 x = 0 x = 0 is integrable.
Flashcard 30: Identify convergence: ∫ 1 ∞ 1 x d x \int_{1}^{\infty} \frac{1}{\sqrt{x}} dx ∫ 1 ∞ x 1 d x . Answer: Diverges. Since p = 1 2 ≤ 1 p = \frac{1}{2} \leq 1 p = 2 1 ≤ 1 , the integral diverges.