Description: Multiplication of two ratios. Theorem I.14 of Apostol p. 18. (Contributed by NM, 16-Feb-1995)
Ref | Expression | ||
---|---|---|---|
Hypotheses | divclz.1 | |- A e. CC |
|
divclz.2 | |- B e. CC |
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divmulz.3 | |- C e. CC |
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divmuldiv.4 | |- D e. CC |
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divmuldiv.5 | |- B =/= 0 |
||
divmuldiv.6 | |- D =/= 0 |
||
Assertion | divmuldivi | |- ( ( A / B ) x. ( C / D ) ) = ( ( A x. C ) / ( B x. D ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | divclz.1 | |- A e. CC |
|
2 | divclz.2 | |- B e. CC |
|
3 | divmulz.3 | |- C e. CC |
|
4 | divmuldiv.4 | |- D e. CC |
|
5 | divmuldiv.5 | |- B =/= 0 |
|
6 | divmuldiv.6 | |- D =/= 0 |
|
7 | 2 5 | pm3.2i | |- ( B e. CC /\ B =/= 0 ) |
8 | 4 6 | pm3.2i | |- ( D e. CC /\ D =/= 0 ) |
9 | divmuldiv | |- ( ( ( A e. CC /\ C e. CC ) /\ ( ( B e. CC /\ B =/= 0 ) /\ ( D e. CC /\ D =/= 0 ) ) ) -> ( ( A / B ) x. ( C / D ) ) = ( ( A x. C ) / ( B x. D ) ) ) |
|
10 | 1 3 7 8 9 | mp4an | |- ( ( A / B ) x. ( C / D ) ) = ( ( A x. C ) / ( B x. D ) ) |