[.(PI / 4),((3 / 4) * PI).] c= ].0,PI.[ by Lm9, Lm10, XXREAL_2:def 12;
hence dom (cot | [.(PI / 4),((3 / 4) * PI).]) = [.(PI / 4),((3 / 4) * PI).] by Th2, RELAT_1:62, XBOOLE_1:1; :: thesis: verum