Metamath Proof Explorer


Theorem refrelcoss3

Description: The class of cosets by R is reflexive, see dfrefrel3 . (Contributed by Peter Mazsa, 30-Jul-2019)

Ref Expression
Assertion refrelcoss3 x dom R y ran R x = y x R y Rel R

Proof

Step Hyp Ref Expression
1 refrelcosslem x dom R x R x
2 idinxpssinxp4 x dom R y dom R x = y x R y x dom R x R x
3 1 2 mpbir x dom R y dom R x = y x R y
4 rncossdmcoss ran R = dom R
5 4 raleqi y ran R x = y x R y y dom R x = y x R y
6 5 ralbii x dom R y ran R x = y x R y x dom R y dom R x = y x R y
7 3 6 mpbir x dom R y ran R x = y x R y
8 relcoss Rel R
9 7 8 pm3.2i x dom R y ran R x = y x R y Rel R