let L be non empty LattStr ; ( ( for v0 being Element of L holds v0 "/\" v0 = v0 ) & ( for v1, v0 being Element of L holds v0 "/\" v1 = v1 "/\" v0 ) & ( for v0 being Element of L holds v0 "\/" v0 = v0 ) & ( for v1, v0 being Element of L holds v0 "\/" v1 = v1 "\/" v0 ) & ( for v2, v1, v0 being Element of L holds ((v0 "\/" v1) "/\" (v2 "\/" v1)) "/\" v1 = v1 ) & ( for v2, v1, v0 being Element of L holds ((v0 "/\" v1) "\/" (v2 "/\" v1)) "\/" v1 = v1 ) & ( for v1, v2, v0 being Element of L holds v0 "/\" (v1 "\/" (v0 "\/" v2)) = v0 ) implies for v0, v1, v2 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2) )
assume A2:
for v0 being Element of L holds v0 "/\" v0 = v0
; ( ex v1, v0 being Element of L st not v0 "/\" v1 = v1 "/\" v0 or ex v0 being Element of L st not v0 "\/" v0 = v0 or ex v1, v0 being Element of L st not v0 "\/" v1 = v1 "\/" v0 or ex v2, v1, v0 being Element of L st not ((v0 "\/" v1) "/\" (v2 "\/" v1)) "/\" v1 = v1 or ex v2, v1, v0 being Element of L st not ((v0 "/\" v1) "\/" (v2 "/\" v1)) "\/" v1 = v1 or ex v1, v2, v0 being Element of L st not v0 "/\" (v1 "\/" (v0 "\/" v2)) = v0 or for v0, v1, v2 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2) )
assume A3:
for v1, v0 being Element of L holds v0 "/\" v1 = v1 "/\" v0
; ( ex v0 being Element of L st not v0 "\/" v0 = v0 or ex v1, v0 being Element of L st not v0 "\/" v1 = v1 "\/" v0 or ex v2, v1, v0 being Element of L st not ((v0 "\/" v1) "/\" (v2 "\/" v1)) "/\" v1 = v1 or ex v2, v1, v0 being Element of L st not ((v0 "/\" v1) "\/" (v2 "/\" v1)) "\/" v1 = v1 or ex v1, v2, v0 being Element of L st not v0 "/\" (v1 "\/" (v0 "\/" v2)) = v0 or for v0, v1, v2 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2) )
assume A4:
for v0 being Element of L holds v0 "\/" v0 = v0
; ( ex v1, v0 being Element of L st not v0 "\/" v1 = v1 "\/" v0 or ex v2, v1, v0 being Element of L st not ((v0 "\/" v1) "/\" (v2 "\/" v1)) "/\" v1 = v1 or ex v2, v1, v0 being Element of L st not ((v0 "/\" v1) "\/" (v2 "/\" v1)) "\/" v1 = v1 or ex v1, v2, v0 being Element of L st not v0 "/\" (v1 "\/" (v0 "\/" v2)) = v0 or for v0, v1, v2 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2) )
assume A5:
for v1, v0 being Element of L holds v0 "\/" v1 = v1 "\/" v0
; ( ex v2, v1, v0 being Element of L st not ((v0 "\/" v1) "/\" (v2 "\/" v1)) "/\" v1 = v1 or ex v2, v1, v0 being Element of L st not ((v0 "/\" v1) "\/" (v2 "/\" v1)) "\/" v1 = v1 or ex v1, v2, v0 being Element of L st not v0 "/\" (v1 "\/" (v0 "\/" v2)) = v0 or for v0, v1, v2 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2) )
assume A6:
for v2, v1, v0 being Element of L holds ((v0 "\/" v1) "/\" (v2 "\/" v1)) "/\" v1 = v1
; ( ex v2, v1, v0 being Element of L st not ((v0 "/\" v1) "\/" (v2 "/\" v1)) "\/" v1 = v1 or ex v1, v2, v0 being Element of L st not v0 "/\" (v1 "\/" (v0 "\/" v2)) = v0 or for v0, v1, v2 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2) )
A8:
for v2, v1, v0 being Element of L holds v1 "/\" ((v0 "\/" v1) "/\" (v2 "\/" v1)) = v1
assume A10:
for v2, v1, v0 being Element of L holds ((v0 "/\" v1) "\/" (v2 "/\" v1)) "\/" v1 = v1
; ( ex v1, v2, v0 being Element of L st not v0 "/\" (v1 "\/" (v0 "\/" v2)) = v0 or for v0, v1, v2 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2) )
A12:
for v2, v1, v0 being Element of L holds v1 "\/" ((v0 "/\" v1) "\/" (v2 "/\" v1)) = v1
assume A14:
for v1, v2, v0 being Element of L holds v0 "/\" (v1 "\/" (v0 "\/" v2)) = v0
; for v0, v1, v2 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2)
A20:
for v100, v102 being Element of L holds v100 "/\" (v102 "\/" v100) = v100
A23:
for v2, v1, v0 being Element of L holds v0 "\/" ((v0 "/\" v1) "\/" (v2 "/\" v0)) = v0
A25:
for v2, v0, v1 being Element of L holds v0 "\/" ((v1 "/\" v0) "\/" (v0 "/\" v2)) = v0
A28:
for v100, v102 being Element of L holds v100 "\/" (v102 "/\" v100) = v100
A32:
for v102, v2, v101, v1 being Element of L holds ((v1 "/\" v101) "\/" (v2 "/\" v101)) "/\" (v101 "/\" (v102 "\/" ((v1 "/\" v101) "\/" (v2 "/\" v101)))) = (v1 "/\" v101) "\/" (v2 "/\" v101)
A35:
for v1, v0, v2 being Element of L holds v0 "/\" (v1 "\/" (v2 "\/" v0)) = v0
A38:
for v102, v101, v1 being Element of L holds (v1 "\/" v101) "\/" (v101 "\/" (v102 "/\" (v1 "\/" v101))) = v1 "\/" v101
A41:
for v1, v0 being Element of L holds v0 "\/" (v0 "/\" v1) = v0
A44:
for v102, v1, v101 being Element of L holds (v101 "/\" v1) "/\" (v101 "/\" (v102 "\/" (v101 "/\" v1))) = v101 "/\" v1
A47:
for v1, v0, v2 being Element of L holds v0 "/\" ((v2 "\/" v0) "\/" v1) = v0
A51:
for v101, v102, v1 being Element of L holds (v1 "/\" v102) "/\" (v101 "\/" v102) = v1 "/\" v102
A55:
for v102, v101, v1 being Element of L holds (v1 "/\" v101) "/\" (v101 "\/" v102) = v1 "/\" v101
A58:
for v2, v1, v0 being Element of L holds v0 "\/" ((v0 "/\" v1) "\/" (v0 "/\" v2)) = v0
A61:
for v102, v2, v101, v1 being Element of L holds ((v1 "/\" v101) "\/" (v101 "/\" v2)) "/\" (v101 "/\" (v102 "\/" ((v1 "/\" v101) "\/" (v101 "/\" v2)))) = (v1 "/\" v101) "\/" (v101 "/\" v2)
A65:
for v0, v1, v2 being Element of L holds (v2 "\/" v1) "\/" (v0 "/\" v1) = v2 "\/" v1
A69:
for v100, v1, v102 being Element of L holds (v100 "/\" (v102 "/\" v1)) "/\" v102 = v100 "/\" (v102 "/\" v1)
A72:
for v0, v2, v1 being Element of L holds v1 "/\" (v0 "/\" (v1 "/\" v2)) = v0 "/\" (v1 "/\" v2)
A76:
for v101, v102 being Element of L holds ((v102 "/\" v101) "\/" (v102 "/\" v101)) "/\" (v101 "/\" v102) = (v102 "/\" v101) "\/" (v102 "/\" v101)
A79:
for v1, v0 being Element of L holds (v0 "/\" v1) "/\" (v1 "/\" v0) = (v0 "/\" v1) "\/" (v0 "/\" v1)
A81:
for v1, v0 being Element of L holds (v0 "/\" v1) "/\" (v1 "/\" v0) = v0 "/\" v1
A84:
for v102, v100, v1 being Element of L holds v100 "\/" (v102 "/\" (v1 "/\" v100)) = v100 "\/" (v1 "/\" v100)
A87:
for v1, v0, v2 being Element of L holds v0 "\/" (v1 "/\" (v2 "/\" v0)) = v0
A90:
for v102, v1, v100 being Element of L holds v100 "\/" (v102 "/\" (v100 "/\" v1)) = v100 "\/" (v100 "/\" v1)
A93:
for v1, v2, v0 being Element of L holds v0 "\/" (v1 "/\" (v0 "/\" v2)) = v0
A95:
for v1, v0, v2 being Element of L holds v0 "\/" ((v2 "/\" v0) "/\" v1) = v0
A99:
for v102, v2, v100, v1 being Element of L holds v100 "\/" (((v1 "/\" v100) "/\" v2) "\/" (v102 "/\" (v100 "\/" ((v1 "/\" v100) "/\" v2)))) = v100 "\/" ((v1 "/\" v100) "/\" v2)
A102:
for v3, v2, v0, v1 being Element of L holds v0 "\/" (((v1 "/\" v0) "/\" v2) "\/" (v3 "/\" v0)) = v0 "\/" ((v1 "/\" v0) "/\" v2)
A104:
for v3, v2, v0, v1 being Element of L holds v0 "\/" (((v1 "/\" v0) "/\" v2) "\/" (v3 "/\" v0)) = v0
A107:
for v102, v0, v1 being Element of L holds (v0 "/\" v1) "/\" ((v1 "/\" v0) "\/" v102) = (v0 "/\" v1) "/\" (v1 "/\" v0)
A110:
for v2, v0, v1 being Element of L holds (v0 "/\" v1) "/\" ((v1 "/\" v0) "\/" v2) = v0 "/\" v1
A113:
for v100, v101, v0 being Element of L holds (v100 "/\" v101) "/\" (v100 "/\" (v0 "\/" v101)) = v100 "/\" v101
A117:
for v100, v2, v102 being Element of L holds (v100 "/\" (v102 "/\" v2)) "/\" (v100 "/\" v102) = v100 "/\" (v102 "/\" v2)
A120:
for v0, v2, v1 being Element of L holds (v0 "/\" v1) "/\" (v0 "/\" (v1 "/\" v2)) = v0 "/\" (v1 "/\" v2)
A123:
for v101, v1, v2, v100 being Element of L holds v100 "\/" ((v100 "/\" v101) "\/" (v1 "/\" (v100 "/\" v2))) = v100
A127:
for v101, v102, v1 being Element of L holds (((v1 "/\" v102) "/\" v101) "\/" (v101 "/\" v102)) "/\" (v101 "/\" v102) = ((v1 "/\" v102) "/\" v101) "\/" (v101 "/\" v102)
A130:
for v2, v1, v0 being Element of L holds (v2 "/\" v1) "/\" (((v0 "/\" v1) "/\" v2) "\/" (v2 "/\" v1)) = ((v0 "/\" v1) "/\" v2) "\/" (v2 "/\" v1)
A133:
for v0, v1, v2 being Element of L holds v0 "/\" v1 = ((v2 "/\" v1) "/\" v0) "\/" (v0 "/\" v1)
A138:
for v101, v3, v100 being Element of L holds ((v100 "/\" v101) "\/" (v101 "/\" (v100 "/\" v3))) "/\" (v101 "/\" v100) = (v100 "/\" v101) "\/" (v101 "/\" (v100 "/\" v3))
A141:
for v1, v2, v0 being Element of L holds (v1 "/\" v0) "/\" ((v0 "/\" v1) "\/" (v1 "/\" (v0 "/\" v2))) = (v0 "/\" v1) "\/" (v1 "/\" (v0 "/\" v2))
A144:
for v0, v2, v1 being Element of L holds v0 "/\" v1 = (v1 "/\" v0) "\/" (v0 "/\" (v1 "/\" v2))
A149:
for v100, v101, v2 being Element of L holds (v100 "/\" v101) "\/" ((v100 "/\" (v2 "\/" v101)) "/\" v101) = (v100 "/\" (v2 "\/" v101)) "/\" v101
A152:
for v0, v1, v2 being Element of L holds (v0 "/\" v1) "\/" (v1 "/\" (v0 "/\" (v2 "\/" v1))) = (v0 "/\" (v2 "\/" v1)) "/\" v1
A154:
for v0, v1, v2 being Element of L holds v1 "/\" v0 = (v0 "/\" (v2 "\/" v1)) "/\" v1
A157:
for v1, v0, v2 being Element of L holds v0 "/\" v1 = v0 "/\" (v1 "/\" (v2 "\/" v0))
A160:
for v1, v0, v2 being Element of L holds v0 "/\" ((v2 "\/" v0) "/\" v1) = v0 "/\" v1
A164:
for v102, v101, v1 being Element of L holds (v1 "/\" v101) "/\" (v101 "/\" v102) = (v1 "/\" v101) "/\" v102
A168:
for v102, v1, v101 being Element of L holds (v101 "/\" v1) "/\" (v101 "/\" v102) = (v101 "/\" v1) "/\" v102
A171:
for v2, v1, v0 being Element of L holds (v0 "/\" v1) "/\" (v1 "/\" v2) = v0 "/\" (v1 "/\" v2)
A173:
for v2, v1, v0 being Element of L holds (v0 "/\" v1) "/\" v2 = v0 "/\" (v1 "/\" v2)
A175:
for v1, v2, v0 being Element of L holds v0 "/\" (v1 "/\" (v0 "/\" v2)) = (v0 "/\" v1) "/\" v2
A177:
for v1, v2, v0 being Element of L holds v1 "/\" (v0 "/\" v2) = (v0 "/\" v1) "/\" v2
A180:
for v0, v2, v1 being Element of L holds v0 "/\" (v1 "/\" v2) = v1 "/\" (v0 "/\" v2)
let v0, v2, v1 be Element of L; (v0 "/\" v2) "/\" v1 = v0 "/\" (v2 "/\" v1)
v1 "/\" (v0 "/\" v2) = v0 "/\" (v1 "/\" v2)
by A180;
then
v1 "/\" (v0 "/\" v2) = v0 "/\" (v2 "/\" v1)
by A3;
hence
(v0 "/\" v2) "/\" v1 = v0 "/\" (v2 "/\" v1)
by A3; verum