Zth = L*s + 1/(1/R1 + 1/R2)
I(s) = U(s)/Zth = (E/s)/Zth = E/(s*(L*s + 1/(1/R1 + 1/R2)))
Lu^(-1) => i(t) = (E*(R1 + R2))/(R1*R2) - (E*L*(R1 + R2)^2)/(R1*R2*exp((R1*R2*t)/(L*R1 + L*R2))*(L*R1 + L*R2))
Avec Rth = R1//R2:
i(t) = E/Rth - E/(Rth*exp((Rth*t)/L))