Theorem fvmpt4

Description: Value of a function given by the maps-to notation. (Contributed by Glauco Siliprandi, 23-Oct-2021)

	Ref	Expression
Assertion	fvmpt4	$$⊢\left(x\in A\wedge B\in C\right)\to \left(x\in A⟼B\right)\left(x\right)=B$$

Proof

Step	Hyp	Ref	Expression
1		eqid	$$⊢\left(x\in A⟼B\right)=\left(x\in A⟼B\right)$$
2	1	fvmpt2	$$⊢\left(x\in A\wedge B\in C\right)\to \left(x\in A⟼B\right)\left(x\right)=B$$