1. The problem statement, all variables and given/known data Basically, I have LQ''(t) + RQ'(t) + (1/C)Q(t)=0, and I'm supposed to "Show that the ration of the charge Q between two successive maxima is given by exp(RTd/2L), where Td is the time between two successive maxima. The natural logarithm of this ration is called the logarithmic decrement. 2. Relevant equations Dunno 3. The attempt at a solution So I got a solution Q(t)=e(-Rt)/(2L) [ C1cos( (√(R2-4L/C) )/(2L)t) + C2sin( (√(R2-4L/C) )/(2L)t). But I can't figure out how to find Td. I mean, I could always find t when dQ/dt=0; but then I'd have to plug two values of t back into Q(t) and find the difference, and ............ So what's the right way to do this?