theorem :: FUZZY_7:45

for a, b, c, d, r being Real st a < b & b < c & c < d holds
TrapezoidalFS (a,b,c,d) = ((AffineMap (0,0)) | (REAL \ ].a,d.[)) +* ((TrapezoidalFS (a,b,c,d)) | [.a,d.])