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## Homework Statement

In an LC-circuit, with:

L = 64 mH

C = 121 nF

where at t=0,

Q = 10*10^-6 C , (the charge on the capasitor)

I = 0,3 A, (the current through the inductor)

Write an expression for the charge on the capacitor and the current through the inductor as a function of time.

## The Attempt at a Solution

I've tried this several times from stratch now, and while I do get an answer, according to the book I'm wrong. The standard form of a solution for Q, is Q = Qm*cos(wt + phi), where phi is the phase displacement. My strategy is to write both the expressions for Q and I, both containing the unknown parameters phi and Qm, and solving the system of two equations with two unknowns.

However, I always get phi = -1,20, whereas the answer in the book is phi = -0,922. I've attached my latest handwritten attempt at a solution, thanks for any help!