Step |
Hyp |
Ref |
Expression |
1 |
|
subcl |
|- ( ( A e. CC /\ B e. CC ) -> ( A - B ) e. CC ) |
2 |
|
subsub2 |
|- ( ( ( A - B ) e. CC /\ C e. CC /\ D e. CC ) -> ( ( A - B ) - ( C - D ) ) = ( ( A - B ) + ( D - C ) ) ) |
3 |
2
|
3expb |
|- ( ( ( A - B ) e. CC /\ ( C e. CC /\ D e. CC ) ) -> ( ( A - B ) - ( C - D ) ) = ( ( A - B ) + ( D - C ) ) ) |
4 |
1 3
|
sylan |
|- ( ( ( A e. CC /\ B e. CC ) /\ ( C e. CC /\ D e. CC ) ) -> ( ( A - B ) - ( C - D ) ) = ( ( A - B ) + ( D - C ) ) ) |
5 |
|
addsub4 |
|- ( ( ( A e. CC /\ D e. CC ) /\ ( B e. CC /\ C e. CC ) ) -> ( ( A + D ) - ( B + C ) ) = ( ( A - B ) + ( D - C ) ) ) |
6 |
5
|
an42s |
|- ( ( ( A e. CC /\ B e. CC ) /\ ( C e. CC /\ D e. CC ) ) -> ( ( A + D ) - ( B + C ) ) = ( ( A - B ) + ( D - C ) ) ) |
7 |
4 6
|
eqtr4d |
|- ( ( ( A e. CC /\ B e. CC ) /\ ( C e. CC /\ D e. CC ) ) -> ( ( A - B ) - ( C - D ) ) = ( ( A + D ) - ( B + C ) ) ) |