I want to get the value of the corresponding parameter t when dil=0 or dvc=0. What method can I use?
sol1 = DSolve[{l il'[t] == vl[t], c vc'[t] == ic[t],
ir[t] == -ic[t] + il[t], vl[t] == 24 - vc[t], vr[t] == vc[t],
vr[t] == r ir[t], il[0] == 0, vc[0] == 0}, {ir[t], il[t], ic[t],
vr[t], vl[t], vc[t]}, t];
{il[t_], vc[t_]} = {il[t], vc[t]} /. sol1[[1]];
pars1 = {r -> 22, l -> 2 10^-1, c -> 1 10^-4};
a = Evaluate[il[t] /. pars1] // Simplify;
b = Evaluate[vc[t] /. pars1] // Simplify;
dil = D[a, t] // Simplify
dvc = D[b, t] // Simplify
