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The integral evaluates to \( \sqrt{x^2 - 16} - 4 \sec^{-1}\left(\frac{x}{4}\right) + C \).
Solución
To evaluate the integral
\[
I = \int \frac{\sqrt{x^2 - 16}}{x} \, dx,
\]
we can use a substitution method.
### Step 1: Substitution
Let's use the substitution \( x = 4 \sec(\theta) \). Then, we have:
\[
dx = 4 \sec(\theta) \tan(\theta) \, d\theta.
\]
### Step 2: Transform the integral
Now, we can rewrite the integral in terms of \(\theta\):
1. Calculate \( \sqrt{x^2 - 16} \):
\[
\sqrt{x^2 - 16} = \sqrt{(4 \sec(\theta))^2 - 16} = \sqrt{16 \sec^2(\theta) - 16} = \sqrt{16(\sec^2(\theta) - 1)} = \sqrt{16 \tan^2(\theta)} = 4 \tan(\theta).
\]
2. Substitute into the integral:
\[
I = \int \frac{4 \tan(\theta)}{4 \sec(\theta)} \cdot 4 \sec(\theta) \tan(\theta) \, d\theta = \int 4 \tan^2(\theta) \, d\theta.
\]
### Step 3: Simplify the integral
Using the identity \( \tan^2(\theta) = \sec^2(\theta) - 1 \), we can rewrite the integral:
\[
I = 4 \int \tan^2(\theta) \, d\theta = 4 \int (\sec^2(\theta) - 1) \, d\theta = 4 \left( \int \sec^2(\theta) \, d\theta - \int 1 \, d\theta \right).
\]
### Step 4: Evaluate the integrals
The integrals can be evaluated as follows:
1. \( \int \sec^2(\theta) \, d\theta = \tan(\theta) + C_1 \).
2. \( \int 1 \, d\theta = \theta + C_2 \).
Thus,
\[
I = 4 \left( \tan(\theta) - \theta \right) + C.
\]
### Step 5: Back-substitution
Now we need to convert back to \(x\):
1. From our substitution \( x = 4 \sec(\theta) \), we have \( \sec(\theta) = \frac{x}{4} \) and thus \( \tan(\theta) = \sqrt{\sec^2(\theta) - 1} = \sqrt{\left(\frac{x}{4}\right)^2 - 1} = \frac{\sqrt{x^2 - 16}}{4} \).
2. Also, \( \theta = \sec^{-1}\left(\frac{x}{4}\right) \).
Putting it all together, we have:
\[
I = 4 \left( \frac{\sqrt{x^2 - 16}}{4} - \sec^{-1}\left(\frac{x}{4}\right) \right) + C = \sqrt{x^2 - 16} - 4 \sec^{-1}\left(\frac{x}{4}\right) + C.
\]
### Final Answer
Thus, the evaluated integral is:
\[
\int \frac{\sqrt{x^2 - 16}}{x} \, dx = \sqrt{x^2 - 16} - 4 \sec^{-1}\left(\frac{x}{4}\right) + C.
\]
Revisado y aprobado por el equipo de tutoría de UpStudy
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