Arguments real_ltr_normlP {x y}.

Lemma lerif_pmul x1 x2 y1 y2 C1 C2 :
0 <= x1 -> 0 <= x2 -> x1 <= y1 ?= iff C1 -> x2 <= y2 ?= iff C2 ->
x1 * x2 <= y1 * y2 ?= iff (y1 * y2 == 0) || C1 && C2.