Selesaikan \( \displaystyle \iint \rho \ \cos \theta \ dp \ d\theta \).
Pembahasan:
\begin{aligned} \iint \rho \ \cos \theta \ dp \ d\theta &= \int \left( \frac{1}{2}\rho^2 \cos \theta + c_1 \right) d\theta \\[8pt] &= \frac{1}{2}\rho^2 \sin \theta + \theta c_1 + c_2 \end{aligned}