I was given a practice problem as listed below. It says that the solution is in the form of a second order differential equation, but I thought that only RLC circuits were 2nd order. Am I missing something or is the textbook solution wrong? The values aren't necessarily important as it is the approach. To clarify the value beings solve for is the voltage at some time t ---> v(t).
node 1: 5cos(t) = v(t)/R + L(di/dt)