Metamath Proof Explorer


Theorem eldmqsres

Description: Elementhood in a restricted domain quotient set. (Contributed by Peter Mazsa, 21-Aug-2020)

Ref Expression
Assertion eldmqsres B V B dom R A / R A u A x x u R B = u R

Proof

Step Hyp Ref Expression
1 elqsg B V B dom R A / R A u dom R A B = u R A
2 eldmres2 u V u dom R A u A x x u R
3 2 elv u dom R A u A x x u R
4 3 anbi1i u dom R A B = u R A u A x x u R B = u R A
5 ecres2 u A u R A = u R
6 5 eqeq2d u A B = u R A B = u R
7 6 pm5.32i u A B = u R A u A B = u R
8 7 anbi2i x x u R u A B = u R A x x u R u A B = u R
9 an21 u A x x u R B = u R A x x u R u A B = u R A
10 an12 u A x x u R B = u R x x u R u A B = u R
11 8 9 10 3bitr4i u A x x u R B = u R A u A x x u R B = u R
12 4 11 bitri u dom R A B = u R A u A x x u R B = u R
13 12 rexbii2 u dom R A B = u R A u A x x u R B = u R
14 1 13 bitrdi B V B dom R A / R A u A x x u R B = u R