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Evaluate the following or show that it diverges. Show your work.

(a) (5 points)
[tex]\[
\left\{\left(\frac{1}{n}\right)^{\frac{1}{n}}\right\}
\][/tex]

(b) (5 points)
[tex]\[
\left\{\int_0^p e^{-x} \, dx\right\}, \, p \in \mathbb{R}
\][/tex]

(c) (5 points)
[tex]\[
\left\{\sqrt{n^2-1}-(n-1)\right\}
\][/tex]


Sagot :

Let's break down each part of the problem and solve them step-by-step.

### Part (a)
Evaluate the limit:
[tex]\[ \lim_{n \to \infty} \left(\frac{1}{n}\right)^{\frac{1}{n}} \][/tex]

1. Start by taking the natural logarithm of the expression:
[tex]\[ \ln\left[\left(\frac{1}{n}\right)^{\frac{1}{n}}\right] = \frac{1}{n} \ln\left(\frac{1}{n}\right) \][/tex]

2. Simplify the inside logarithm:
[tex]\[ \frac{1}{n} \ln\left(\frac{1}{n}\right) = \frac{1}{n} \cdot (-\ln(n)) = -\frac{\ln(n)}{n} \][/tex]

3. Evaluate the limit of the simplified expression as [tex]\( n \to \infty \)[/tex]:
[tex]\[ \lim_{n \to \infty} -\frac{\ln(n)}{n} \][/tex]

It's known that [tex]\(\frac{\ln(n)}{n} \)[/tex] approaches 0 as [tex]\( n \to \infty \)[/tex]:

[tex]\[ \lim_{n \to \infty} -\frac{\ln(n)}{n} = 0 \][/tex]

4. Therefore, the limit of the original expression becomes:
[tex]\[ e^0 = 1 \][/tex]

So, the limit is:
[tex]\[ 1 \][/tex]

### Part (b)
Evaluate the integral:
[tex]\[ \int_0^p e^{-x} \, dx \][/tex]

1. Compute the integral of [tex]\( e^{-x} \)[/tex]:
[tex]\[ \int e^{-x} \, dx = -e^{-x} + C \][/tex]

2. Evaluate the integral from 0 to [tex]\( p \)[/tex]:
[tex]\[ \left[ -e^{-x} \right]_{0}^{p} = -e^{-p} - (-e^{0}) \][/tex]

3. Simplify the expression:
[tex]\[ -e^{-p} + 1 = 1 - e^{-p} \][/tex]

So, the value of the integral is:
[tex]\[ 1 - e^{-p} \][/tex]

### Part (c)
Evaluate the limit:
[tex]\[ \lim_{n \to \infty} \left( \sqrt{n^2 - 1} - (n - 1) \right) \][/tex]

1. Rewrite the expression inside the limit:
[tex]\[ \sqrt{n^2 - 1} - (n - 1) = \sqrt{n^2 - 1} - n + 1 \][/tex]

2. Factor out [tex]\( n \)[/tex] from the square root using the expansion [tex]\(\sqrt{n^2 - 1} \approx n \sqrt{1 - \frac{1}{n^2}}\)[/tex]:
[tex]\[ \sqrt{n^2 - 1} \approx n \sqrt{1 - \frac{1}{n^2}} \approx n \left(1 - \frac{1}{2n^2}\right) \][/tex]

3. Substitute this approximation back into the original expression:
[tex]\[ n \left(1 - \frac{1}{2n^2}\right) - n + 1 = n - \frac{1}{2n} - n + 1 = 1 - \frac{1}{2n} \][/tex]

4. As [tex]\( n \to \infty \)[/tex]:
[tex]\[ \frac{1}{2n} \approaches 0 \][/tex]

So, the limit is:
[tex]\[ 1 \][/tex]

### Summary
(a) [tex]\[ \lim_{n \to \infty} \left(\frac{1}{n}\right)^{\frac{1}{n}} = 1 \][/tex]

(b) [tex]\[ \int_0^p e^{-x} \, dx = 1 - e^{-p} \][/tex]

(c) [tex]\[ \lim_{n \to \infty} \left( \sqrt{n^2 - 1} - (n - 1) \right) = 1 \][/tex]