| Step | Hyp | Ref | Expression |
| 1 |
|
axext |
upto (suc a) == a ; upto a -> upto (suc a) = a ; upto a |
| 2 |
|
bitr4 |
(x e. upto (suc a) <-> x < suc a) -> (x e. a ; upto a <-> x < suc a) -> (x e. upto (suc a) <-> x e. a ; upto a) |
| 3 |
|
elupto |
x e. upto (suc a) <-> x < suc a |
| 4 |
2, 3 |
ax_mp |
(x e. a ; upto a <-> x < suc a) -> (x e. upto (suc a) <-> x e. a ; upto a) |
| 5 |
|
bitr4 |
(x e. a ; upto a <-> x = a \/ x e. upto a) -> (x < suc a <-> x = a \/ x e. upto a) -> (x e. a ; upto a <-> x < suc a) |
| 6 |
|
elins |
x e. a ; upto a <-> x = a \/ x e. upto a |
| 7 |
5, 6 |
ax_mp |
(x < suc a <-> x = a \/ x e. upto a) -> (x e. a ; upto a <-> x < suc a) |
| 8 |
|
bitr3 |
(x <= a <-> x < suc a) -> (x <= a <-> x = a \/ x e. upto a) -> (x < suc a <-> x = a \/ x e. upto a) |
| 9 |
|
leltsuc |
x <= a <-> x < suc a |
| 10 |
8, 9 |
ax_mp |
(x <= a <-> x = a \/ x e. upto a) -> (x < suc a <-> x = a \/ x e. upto a) |
| 11 |
|
bitr4 |
(x <= a <-> x < a \/ x = a) -> (x = a \/ x e. upto a <-> x < a \/ x = a) -> (x <= a <-> x = a \/ x e. upto a) |
| 12 |
|
leloe |
x <= a <-> x < a \/ x = a |
| 13 |
11, 12 |
ax_mp |
(x = a \/ x e. upto a <-> x < a \/ x = a) -> (x <= a <-> x = a \/ x e. upto a) |
| 14 |
|
bitr |
(x = a \/ x e. upto a <-> x e. upto a \/ x = a) -> (x e. upto a \/ x = a <-> x < a \/ x = a) -> (x = a \/ x e. upto a <-> x < a \/ x = a) |
| 15 |
|
orcomb |
x = a \/ x e. upto a <-> x e. upto a \/ x = a |
| 16 |
14, 15 |
ax_mp |
(x e. upto a \/ x = a <-> x < a \/ x = a) -> (x = a \/ x e. upto a <-> x < a \/ x = a) |
| 17 |
|
oreq1 |
(x e. upto a <-> x < a) -> (x e. upto a \/ x = a <-> x < a \/ x = a) |
| 18 |
|
elupto |
x e. upto a <-> x < a |
| 19 |
17, 18 |
ax_mp |
x e. upto a \/ x = a <-> x < a \/ x = a |
| 20 |
16, 19 |
ax_mp |
x = a \/ x e. upto a <-> x < a \/ x = a |
| 21 |
13, 20 |
ax_mp |
x <= a <-> x = a \/ x e. upto a |
| 22 |
10, 21 |
ax_mp |
x < suc a <-> x = a \/ x e. upto a |
| 23 |
7, 22 |
ax_mp |
x e. a ; upto a <-> x < suc a |
| 24 |
4, 23 |
ax_mp |
x e. upto (suc a) <-> x e. a ; upto a |
| 25 |
24 |
ax_gen |
A. x (x e. upto (suc a) <-> x e. a ; upto a) |
| 26 |
25 |
conv eqs |
upto (suc a) == a ; upto a |
| 27 |
1, 26 |
ax_mp |
upto (suc a) = a ; upto a |