Desenezi conul ocupat de apa si in triunghiul format de inaltime, generatoare si raza, unghiul de la varf este de 60 grade.
[tex]tg60^{\circ}=\dfrac Rh\Rightarrow \sqrt3=\dfrac R1\Rightarrow R=1\ dm
[/tex]
[tex]V_1=\dfrac{\pi R^2h}{3}=\pi\ dm^3=\pi l[/tex]
[tex]\dfrac{V_2}{V_1}=\left(\dfrac{h_2}{h_1}\right)^3=\left(\dfrac21\right)^3\Rightarrow V_2=2^3\pi\ l[/tex]
[tex]\dfrac{V_3}{V_1}=\left(\dfrac{h_3}{h_1}\right)^3=\left(\dfrac31\right)^3\Rightarrow V_3=3^3\pi\ l[/tex]
Asemanator se obtine [tex]V_n=n^3\pi\ l[/tex]