what's negative frequency in analysis of s domain and w domain

what's negative frequency???

can we say s=-3 in example bode plot !!!!!
or we can say it's unstable at w=-3 rad/s

that's I mean is there negative frequency????????????

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 Recognitions: Homework Help Where have you seen a negative frequency occur? Something like this?
 yes.

Recognitions:
Homework Help

what's negative frequency in analysis of s domain and w domain

 Negative frequency is nothing but phase reversal. eg. sin(2pi(-f)t)=-sin(2pi(f)t)

Recognitions:
 Quote by okami11408 eg. cos(2pi(-f)t)=-cos(2pi(f)t)
That's not even close to correct.

 Im sorry its sine not cosine.

Recognitions:
$$V(t)=\Re\{[\cos(\omega t)+j\sin(\omega t)]\exp(j\omega_0 t)\}$$versus
$$V(t)=\Re\{\cos(\omega t)-j\sin(\omega t)]\exp(j\omega_0 t)\}$$