Obliczam l
[tex]P=\frac{l^2\sqrt3}{4}\\\\\frac{l^2\sqrt3}{4}=36\sqrt3\ \ \ |:\sqrt3\\\\\frac{l^2}{4}=36\ \ \ |\cdot4\\\\l^2=144\\\\l=\sqrt{144}\\\\l=12[/tex]
Obliczam r
r=l:2
r=6cm
Obliczam pole
[tex]P_c=\pi r(r+l)\\\\P_c=6\cdot(6+12)\pi\\\\P_c=6\cdot18\pi\\\\P_c=108\pi[/tex]