| Step |
Hyp |
Ref |
Expression |
| 1 |
|
dfifp2 |
|- ( if- ( ph , ( ps \/ ch ) , ( th \/ ta ) ) <-> ( ( ph -> ( ps \/ ch ) ) /\ ( -. ph -> ( th \/ ta ) ) ) ) |
| 2 |
|
df-or |
|- ( ( ps \/ ch ) <-> ( -. ps -> ch ) ) |
| 3 |
2
|
imbi2i |
|- ( ( ph -> ( ps \/ ch ) ) <-> ( ph -> ( -. ps -> ch ) ) ) |
| 4 |
|
df-or |
|- ( ( th \/ ta ) <-> ( -. th -> ta ) ) |
| 5 |
4
|
imbi2i |
|- ( ( -. ph -> ( th \/ ta ) ) <-> ( -. ph -> ( -. th -> ta ) ) ) |
| 6 |
3 5
|
anbi12i |
|- ( ( ( ph -> ( ps \/ ch ) ) /\ ( -. ph -> ( th \/ ta ) ) ) <-> ( ( ph -> ( -. ps -> ch ) ) /\ ( -. ph -> ( -. th -> ta ) ) ) ) |
| 7 |
|
ifpimimb |
|- ( if- ( ph , ( -. ps -> ch ) , ( -. th -> ta ) ) <-> ( if- ( ph , -. ps , -. th ) -> if- ( ph , ch , ta ) ) ) |
| 8 |
|
dfifp2 |
|- ( if- ( ph , ( -. ps -> ch ) , ( -. th -> ta ) ) <-> ( ( ph -> ( -. ps -> ch ) ) /\ ( -. ph -> ( -. th -> ta ) ) ) ) |
| 9 |
|
imor |
|- ( ( if- ( ph , -. ps , -. th ) -> if- ( ph , ch , ta ) ) <-> ( -. if- ( ph , -. ps , -. th ) \/ if- ( ph , ch , ta ) ) ) |
| 10 |
|
ifpnot23d |
|- ( -. if- ( ph , -. ps , -. th ) <-> if- ( ph , ps , th ) ) |
| 11 |
10
|
orbi1i |
|- ( ( -. if- ( ph , -. ps , -. th ) \/ if- ( ph , ch , ta ) ) <-> ( if- ( ph , ps , th ) \/ if- ( ph , ch , ta ) ) ) |
| 12 |
9 11
|
bitri |
|- ( ( if- ( ph , -. ps , -. th ) -> if- ( ph , ch , ta ) ) <-> ( if- ( ph , ps , th ) \/ if- ( ph , ch , ta ) ) ) |
| 13 |
7 8 12
|
3bitr3i |
|- ( ( ( ph -> ( -. ps -> ch ) ) /\ ( -. ph -> ( -. th -> ta ) ) ) <-> ( if- ( ph , ps , th ) \/ if- ( ph , ch , ta ) ) ) |
| 14 |
1 6 13
|
3bitri |
|- ( if- ( ph , ( ps \/ ch ) , ( th \/ ta ) ) <-> ( if- ( ph , ps , th ) \/ if- ( ph , ch , ta ) ) ) |