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Description: The natural logarithm is one-to-one. (Contributed by SN, 25-Apr-2025)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | log11d.a | |- ( ph -> A e. CC ) |
|
| log11d.b | |- ( ph -> B e. CC ) |
||
| log11d.1 | |- ( ph -> A =/= 0 ) |
||
| log11d.2 | |- ( ph -> B =/= 0 ) |
||
| Assertion | log11d | |- ( ph -> ( ( log ` A ) = ( log ` B ) <-> A = B ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | log11d.a | |- ( ph -> A e. CC ) |
|
| 2 | log11d.b | |- ( ph -> B e. CC ) |
|
| 3 | log11d.1 | |- ( ph -> A =/= 0 ) |
|
| 4 | log11d.2 | |- ( ph -> B =/= 0 ) |
|
| 5 | fveq2 | |- ( ( log ` A ) = ( log ` B ) -> ( exp ` ( log ` A ) ) = ( exp ` ( log ` B ) ) ) |
|
| 6 | eflog | |- ( ( A e. CC /\ A =/= 0 ) -> ( exp ` ( log ` A ) ) = A ) |
|
| 7 | 1 3 6 | syl2anc | |- ( ph -> ( exp ` ( log ` A ) ) = A ) |
| 8 | eflog | |- ( ( B e. CC /\ B =/= 0 ) -> ( exp ` ( log ` B ) ) = B ) |
|
| 9 | 2 4 8 | syl2anc | |- ( ph -> ( exp ` ( log ` B ) ) = B ) |
| 10 | 7 9 | eqeq12d | |- ( ph -> ( ( exp ` ( log ` A ) ) = ( exp ` ( log ` B ) ) <-> A = B ) ) |
| 11 | 5 10 | imbitrid | |- ( ph -> ( ( log ` A ) = ( log ` B ) -> A = B ) ) |
| 12 | fveq2 | |- ( A = B -> ( log ` A ) = ( log ` B ) ) |
|
| 13 | 11 12 | impbid1 | |- ( ph -> ( ( log ` A ) = ( log ` B ) <-> A = B ) ) |