Question

Calculate the time, t when there is maximum charge, q .

q = 10(1-e*(-3t)(cos 3t+ sin 3t))
current, i = 60e*(-3t)sin 3t

so when there is maximum charge , i = 0
60e*(-3t)sin3t = 0
how do you solve for t from here ?

Answer 1

60e^(-3t) is always >0, so you just find when sin(3t)=0

Answer 2

3t=Pi*n where n is an integer

t=(Pi*n)/3 for any integer n