suppose we have a RC low Pass filter... the phase response of Vo/Vin of the circuit goes from 0 to -90 in the stopband...

my question is as follows... if we have an input sinwave Asin(wt) with (phase 0 deg) of a particular frequency ( assume it is exactly at the cut-off frequency of the lowpass), so we would have a phase of -45..

the output would be A'sin(wt +phi) where A' is the scaled amplitude and phi is the phase shift....

would the output, in this case, be A'sin(wt-45) ? if that is the case, doesn't that mean that the output is actually leading the input by 45 degrees (which obviously doesn't make sense? where did i go wrong in my analysis...

Thanks guys