Integration of a pair of reflected endpoint pieces and a middle piece #
theorem
ProbabilityTheory.Copula.RankRegion.XiRho.Support.integral_unit_three_pieces
{c : ℝ}
(hc0 : 0 ≤ c)
(hc1 : c ≤ 1 / 2)
(f g h : ℝ → ℝ)
(hf : Continuous f)
(hg : Continuous g)
(hh : Continuous h)
: