theorem Th25: :: FUZZY_9:23

for a, b, c, r being Real
for f being Function of REAL,REAL st a < b & b < c & r <> 0 & ( for x being Real holds f . x = (r (#) (TriangularFS (a,b,c))) . x ) holds
centroid (f,['a,c']) = ((a + b) + c) / 3