let D be non empty set ; :: thesis: for d being Element of D
for F being BinOp of D st F is having_a_unity & F is associative & F is having_an_inverseOp holds
( F . ((the_inverseOp_wrt F) . d),d = the_unity_wrt F & F . d,((the_inverseOp_wrt F) . d) = the_unity_wrt F )
let d be Element of D; :: thesis: for F being BinOp of D st F is having_a_unity & F is associative & F is having_an_inverseOp holds
( F . ((the_inverseOp_wrt F) . d),d = the_unity_wrt F & F . d,((the_inverseOp_wrt F) . d) = the_unity_wrt F )
let F be BinOp of D; :: thesis: ( F is having_a_unity & F is associative & F is having_an_inverseOp implies ( F . ((the_inverseOp_wrt F) . d),d = the_unity_wrt F & F . d,((the_inverseOp_wrt F) . d) = the_unity_wrt F ) )
assume ( F is having_a_unity & F is associative & F is having_an_inverseOp ) ; :: thesis: ( F . ((the_inverseOp_wrt F) . d),d = the_unity_wrt F & F . d,((the_inverseOp_wrt F) . d) = the_unity_wrt F )
then the_inverseOp_wrt F is_an_inverseOp_wrt F by Def3;
hence ( F . ((the_inverseOp_wrt F) . d),d = the_unity_wrt F & F . d,((the_inverseOp_wrt F) . d) = the_unity_wrt F ) by Def1; :: thesis: verum