reserve x for Real;

theorem
  0 < PI/2 & PI/2 < PI & 0 < PI & -PI/2 < PI/2 & PI < 2*PI & PI/2 < 3/2*
PI & -PI/2 < 0 & 0 < 2*PI & PI < 3/2*PI & 3/2*PI < 2*PI & 0 < 3/2*PI by Lm2,Lm3
