y= 0

_x=\(\frac{\int_l^{ }\ x\ dl}{\int_l^{ }x\ dl}\)                                   

 x= r cos  θ

y= r sen  θ

dl= \(\sqrt{dx^2+dy^2}\) = \(r^2\left(sen^2\theta\ d\theta^2\right)+r^2\left(\cos^2d\theta^2\right)\)

dx=- r sen  θ  =\(\sqrt{r^2d\theta^2\left(sen^2\theta+\cos^2\theta\right)}\)

dy= r cos θ  d θ  =r θ

=\(\frac{\int_{\frac{-2\Pi}{3}}^{\frac{2\Pi}{3}}r\ \cos\theta\ d\theta}{\int_{\frac{-2\Pi}{3}}^{\frac{2\Pi}{3}}r\ d\theta}\) =\(\frac{r^2\int_{\frac{-2\Pi}{3}}^{\frac{2\Pi}{3}}\cos\theta\ d\theta}{r\int_{\frac{-2\Pi}{3}}^{\frac{-2\Pi}{3}}d\theta}\)

= \(\frac{r\ sen\ \theta\left|\frac{\frac{2\Pi}{3}}{\frac{-2\Pi}{3}}\right|}{\theta\left|\frac{\frac{2\Pi}{3}}{\frac{-2\Pi}{3}}\right|}\)= \(\frac{r\left[0.0866+0.866\right]}{\frac{4\Pi}{3}}\) =\(\frac{300mm\left[1.732\right]}{4.189}\)=  124 mm