theorem Th20: :: FUZZY_9:27

for a, b, c, d being Real st a < b & b < c & c < d holds
for x being object st x in [.a,b.] holds
(TrapezoidalFS (a,b,c,d)) . x = (AffineMap ((1 / (b - a)),(- (a / (b - a))))) . x