theorem welfare_eq_kl {z : ℝ} (_hz : 0 < z) : welfareDistanceFn z = klDivExp (1 / z) 1 := by simp only [welfareDistanceFn, klDivExp, div_one, one_div, Real.log_inv, inv_inv] ring
thesis/CESProofs/Foundations/InformationGeometry.lean:104
Information Geometry of CES: