:: deftheorem defines [. SPPOL_2:def 3 :
for r1, r2, r19, r29 being Real holds [.r1,r2,r19,r29.] = ((LSeg (|[r1,r19]|,|[r1,r29]|)) \/ (LSeg (|[r1,r29]|,|[r2,r29]|))) \/ ((LSeg (|[r2,r29]|,|[r2,r19]|)) \/ (LSeg (|[r2,r19]|,|[r1,r19]|)));