The phase shift of the co-sine function relative to the sine function is +90°. It follows that, for two sinusoidal signals F and G with same frequency and amplitudes A and B , and G has phase shift +90° relative to F , the sum F + G is a sinusoidal signal with the same frequency, with amplitude C and phase shift − − 90 ∘ ∘ < φ φ < + 90 ∘ ∘ from F , such that C = A 2 + B 2 and sin ⁡ ⁡ ( φ φ ) = B / C .