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Metamath Proof Explorer
Description: The distance function of a metric space is nonnegative. (Contributed by NM, 27-Aug-2006) (Revised by Mario Carneiro, 14-Aug-2015)
|
|
Ref |
Expression |
|
Assertion |
metge0 |
⊢ ( ( 𝐷 ∈ ( Met ‘ 𝑋 ) ∧ 𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋 ) → 0 ≤ ( 𝐴 𝐷 𝐵 ) ) |
Proof
| Step |
Hyp |
Ref |
Expression |
| 1 |
|
metxmet |
⊢ ( 𝐷 ∈ ( Met ‘ 𝑋 ) → 𝐷 ∈ ( ∞Met ‘ 𝑋 ) ) |
| 2 |
|
xmetge0 |
⊢ ( ( 𝐷 ∈ ( ∞Met ‘ 𝑋 ) ∧ 𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋 ) → 0 ≤ ( 𝐴 𝐷 𝐵 ) ) |
| 3 |
1 2
|
syl3an1 |
⊢ ( ( 𝐷 ∈ ( Met ‘ 𝑋 ) ∧ 𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋 ) → 0 ≤ ( 𝐴 𝐷 𝐵 ) ) |