theorem Th10:
for
N,
M being
ExtNat holds
( not
N <= M + 1 or
N <= M or
N = M + 1 )
theorem
for
N,
M being
ExtNat st
N <= M &
M <= N + 1 & not
N = M holds
M = N + 1
theorem
for
N,
M being
ExtNat st
N * M = 1 holds
N = 1
theorem
for
N,
M,
K being
ExtNat holds
K * (N + M) = (K * N) + (K * M)
theorem Th8:
for
x,
y,
z being
object holds
(
dom <%x,y,z%> = {0,1,2} &
rng <%x,y,z%> = {x,y,z} )