The ratio x max / x min = 2 γ γ is a convenient parameter to characterize the amplitude of pulsation. Using this, we can express the median value δ δ = x max − − x min 1 as δ δ = ln ⁡ ⁡ sin ⁡ ⁡ ( γ γ ) γ γ ; and the energy E = E ( γ γ ) = γ γ tanh ⁡ ⁡ ( γ γ ) + ln ⁡ ⁡ sinh ⁡ ⁡ γ γ γ γ − − 1 is also an elementary function of γ γ .