I can't find the phase shift of an RC low pass filter.?

I am stuck on this problem any help or direction would be appreciated. It says in the following circuit the input voltage vi(t) = sin(wt). What is phase shift of Vo/Vi (w) when absolute value of |Vo(w)/Vi(w)| = -3.01dB. Resistor = 100 ohms and capacitor = 1uF in series. I know the equation needs to be derived from 1/sC/(1+(1/sC)) and from there I insert complex j for s and I get 1/(1+jwRC). Where I think I am lost is where do I go from here do I set the equation equal to -3.01dB which I believe is .707 unless I am wrong and solve for w(omega). Any help would be appreciated.