Black-Leff: E_max=τ/(τ+1); EC_50=K_A/(τ+1); E(EC_50)=τ/[2(τ+1)]; low-A series E≈τA/K_A

Sympy-exact symbolic witness of the Black-Leff operational model canonical asymptotes and EC_50 expressions. Setup: τ, A, K_A, E — all positive symbols. Canonical fractional-response form: E = A·τ/(A·τ + A + K_A) (sympy canonical…