Transcript text: \(\int 8 x \cos (5 x) \mathrm{d} x\)
Solution
Solution Steps
Step 1: Integration by Parts
To solve the integral \(\int 8 x \cos (5 x) \, dx\), we apply the integration by parts formula:
\[
\int u \, dv = uv - \int v \, du
\]
We choose \(u = 8x\) and \(dv = \cos(5x) \, dx\). Then, we compute \(du\) and \(v\):
\[
du = 8 \, dx, \quad v = \frac{1}{5} \sin(5x)
\]
Step 2: Applying the Formula
Substituting \(u\), \(du\), \(v\), and \(dv\) into the integration by parts formula gives:
\[
\int 8 x \cos(5 x) \, dx = 8x \cdot \frac{1}{5} \sin(5x) - \int \frac{1}{5} \sin(5x) \cdot 8 \, dx
\]
This simplifies to:
\[
\frac{8}{5} x \sin(5x) - \frac{8}{5} \int \sin(5x) \, dx
\]
Step 3: Integrating the Remaining Integral
The integral \(\int \sin(5x) \, dx\) can be computed as:
\[
\int \sin(5x) \, dx = -\frac{1}{5} \cos(5x)
\]
Thus, substituting this back into our expression gives:
\[
\frac{8}{5} x \sin(5x) + \frac{8}{25} \cos(5x) + C
\]
Final Answer
The final result of the integral \(\int 8 x \cos(5 x) \, dx\) is:
\[
\boxed{\frac{8}{5} x \sin(5x) + \frac{8}{25} \cos(5x) + C}
\]