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Description: A function's value belongs to its codomain. (Contributed by Mario Carneiro, 29-Dec-2016)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | ffvelcdmd.1 | ⊢ ( 𝜑 → 𝐹 : 𝐴 ⟶ 𝐵 ) | |
| ffvelcdmd.2 | ⊢ ( 𝜑 → 𝐶 ∈ 𝐴 ) | ||
| Assertion | ffvelcdmd | ⊢ ( 𝜑 → ( 𝐹 ‘ 𝐶 ) ∈ 𝐵 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | ffvelcdmd.1 | ⊢ ( 𝜑 → 𝐹 : 𝐴 ⟶ 𝐵 ) | |
| 2 | ffvelcdmd.2 | ⊢ ( 𝜑 → 𝐶 ∈ 𝐴 ) | |
| 3 | 1 | ffvelcdmda | ⊢ ( ( 𝜑 ∧ 𝐶 ∈ 𝐴 ) → ( 𝐹 ‘ 𝐶 ) ∈ 𝐵 ) |
| 4 | 2 3 | mpdan | ⊢ ( 𝜑 → ( 𝐹 ‘ 𝐶 ) ∈ 𝐵 ) |