theorem Th29: :: CAT_4:29

for C being Cartesian_category
for a being Object of C holds
( (lambda a) * (lambda' a) = id a & (lambda' a) * (lambda a) = id (([1] C) [x] a) & (rho a) * (rho' a) = id a & (rho' a) * (rho a) = id (a [x] ([1] C)) )