[tex]\displaystyle\\\eta\%=\frac{L_u}{L_c} =\frac{L_u}{L_c}=\frac{Gh}{Fl}=\frac{mgh}{\bigg(G_t+f_f\bigg)l}=\frac{mgh}{\bigg(Gsin\alpha+\frac{1}{8}G\bigg)l}=\\\frac{mgh}{\bigg(\frac{2}{3}G+\frac{1}{8}G\bigg)l}=\frac{mgh}{\frac{19}{24}Gl}=\boxed{\it\frac{mgh}{\frac{19}{24}mgl}}.\\facem~inlocuirea~numerica \implies \eta \%=0,84 \implies \boxed{\it\eta =84\%}.[/tex]
