Now, this is very easy problem, since I=Q/T it means that i have effective value of current. Now i only need it's phase, since passive element is capacitor it means that current is π/2 "ahead" of voltage so it's phase should be φ=θ+π/2 so

i(t)=Qsqrt(2)/T cos(ωt+θ+π/2). But if i look at the picture the direction of current opposes direction of voltage, does it means that this is not the correct phase of current, because, as far as i know, it works this way if directions are the same?