Weibull: F=1−exp(−(D/α)^β); LD_50=α·log(2)^{1/β}; at β=1: LD_50=α·ln2; F(α)=1−1/e

Sympy-exact symbolic witness of the Weibull dose-response canonical form, LD_50 identity, and characteristic-dose anchor. Setup: D, α, β — all positive symbols. Weibull CDF: F(D) = 1 − exp(−(D/α)^β) (sympy canonical '1 -…