 However, in other forms of flight other values are found.Intuitively the ratio measures the steepness of the strokes, viewed from the side (e.g., assuming movement through a stationary fluid) – "f" is the stroke frequency, "A" is the amplitude, so the numerator "fA" is half the vertical speed of the wing tip, while the denominator "V" is the horizontal speed.Thus the graph of the wing tip forms an approximate sinusoid with aspect (maximal slope) twice the Strouhal constant.