let C be Category; for a being Object of C
for m being Morphism of (a -SliceCat C) holds
( m = [[(m `11),(m `12)],(m `2)] & dom (m `2) = cod (m `11) & (m `2) (*) (m `11) = m `12 & dom m = m `11 & cod m = m `12 )
let o be Object of C; for m being Morphism of (o -SliceCat C) holds
( m = [[(m `11),(m `12)],(m `2)] & dom (m `2) = cod (m `11) & (m `2) (*) (m `11) = m `12 & dom m = m `11 & cod m = m `12 )
let m be Morphism of (o -SliceCat C); ( m = [[(m `11),(m `12)],(m `2)] & dom (m `2) = cod (m `11) & (m `2) (*) (m `11) = m `12 & dom m = m `11 & cod m = m `12 )
consider a, b being Element of o Hom , f being Morphism of C such that
A1:
m = [[a,b],f]
and
A2:
dom f = cod a
and
A3:
f (*) a = b
by Def12;
A4:
m `11 = a
by A1, MCART_1:85;
m `12 = b
by A1, MCART_1:85;
hence
( m = [[(m `11),(m `12)],(m `2)] & dom (m `2) = cod (m `11) & (m `2) (*) (m `11) = m `12 & dom m = m `11 & cod m = m `12 )
by A1, A2, A3, A4, Th2; verum