The negative-gain op amp circuit is supposed to reverse the sign of \mathbf{v}_\mathbf{s} i. e \mathbf{v}_\mathbf{0} is equal to \mathbf{v}_\mathbf{s} multiplied by a negative gain of the op amp. Do you observe this in your measurement of \mathbf{v}_0? If not explain why the negative gain op amp circuit does not invert the sinusoidal input voltage.