Current in an ac circuit is given byI=3 sin ωt+4 cosωt, then

i=3 sin ωt+4 cos ωt=535 sin ωt+45 cos ωt=5sin ωt+δ        ......irms value = 52AMean value=2πi0=10πAIf voltage applied is V=Vm sin ωt then I, given by Eq. (i), indicates that it is ahead of V by δ where 0 < δ < 90 whichindicates that the circuit contains R and C.If we find average value for the first half period (0 to T/2), then it will be 6π/A. But for different time interval, it will bedifferent.