Metamath Proof Explorer


Theorem fdmd

Description: Deduction form of fdm . The domain of a mapping. (Contributed by Glauco Siliprandi, 26-Jun-2021)

Ref Expression
Hypothesis fdmd.1 φ F : A B
Assertion fdmd φ dom F = A

Proof

Step Hyp Ref Expression
1 fdmd.1 φ F : A B
2 fdm F : A B dom F = A
3 1 2 syl φ dom F = A