I want to find frequency by using phase of the signal.But, if the phase has got an error of suppose +2degrees, I am detecting a phase of 359 deg as 1 deg. how to resolve this issue. can someone please help me.
Is to (a) sample however much of the waveform you can, then (b) apply some algorithm which finds how to match it to a sinewave at the correct frequency and phase.
There is an axiom that says if you draw three random points, there is one and only one circle which contains those points. I imagine the same applies to a sinewave, since it is closely related to a circle.