According to Euler’s equation, sines and cosines are defined as follows: the cosine signal consists of a positive and a negative frequency component, both with real, positive, and equal amplitudes. The effect of phase rotating a signal is the positive frequency components rotate in a positive direction, negative frequency components rotate in a negative direction. This becomes more clear when looking at the relationship of the sine to the cosine. The sine signal is the cosine signal, rotated -90 degrees. The sine signal therefore consists of a positive frequency component with a negative imaginary amplitude, and a negative frequency component with a positive imaginary amplitude.