Find the area between the circles $x^{2} + y^{2} = 4$ and $x^{2} + y^{2} = 6x$ using polar coordinates.

---

I have found that the equation of the first circle, call it $C\_1$, is $r=2$ on the other hand, for $C\_2$, I get that its equation is $r = 6cos{\theta}$. Then, to find the bounds of integration, I have found that their angle of intersection should be $\theta = \arccos(1/3)$ and $\theta = -\arccos(1/3)$. Then, to set up the double integral:

$A= \displaystyle\int\_{-\arccos(1/3)}^{\arccos(1/3)} \displaystyle\int\_{6\cos{\theta}}^2 \mathrm{r}\,\mathrm{d}r\, \mathrm{d}{\theta}$

However, when evaluating this integral with the calculator, I get a negative value. What would be the problem in this case? Thanks in advance for your help.