R = 125 ohms, L = 200 mH, C = 5 uF, initial current in L is -0.3A, and initial voltage across C is 25V.
v(t) = (Bcos(wt)+Csin(wt))e^(-at)
The Attempt at a Solution
I've solved for v(t) t>0 and got 25e^(-800t)(cos(600t)+ (4/3)sin(600t)). The second part is to solve for iL for t>0. In class, we've been solved for iL using iL+iR+iC = 0 →iL = -iR-iC but I want to solve for iL using v(t) = L*di/dt and I can't get the same answer as the other method. Is this not valid for this case? Thanks!