Step |
Hyp |
Ref |
Expression |
1 |
|
evpmval.1 |
⊢ 𝐴 = ( pmEven ‘ 𝐷 ) |
2 |
|
elex |
⊢ ( 𝐷 ∈ 𝑉 → 𝐷 ∈ V ) |
3 |
|
fveq2 |
⊢ ( 𝑑 = 𝐷 → ( pmSgn ‘ 𝑑 ) = ( pmSgn ‘ 𝐷 ) ) |
4 |
3
|
cnveqd |
⊢ ( 𝑑 = 𝐷 → ◡ ( pmSgn ‘ 𝑑 ) = ◡ ( pmSgn ‘ 𝐷 ) ) |
5 |
4
|
imaeq1d |
⊢ ( 𝑑 = 𝐷 → ( ◡ ( pmSgn ‘ 𝑑 ) “ { 1 } ) = ( ◡ ( pmSgn ‘ 𝐷 ) “ { 1 } ) ) |
6 |
|
df-evpm |
⊢ pmEven = ( 𝑑 ∈ V ↦ ( ◡ ( pmSgn ‘ 𝑑 ) “ { 1 } ) ) |
7 |
|
fvex |
⊢ ( pmSgn ‘ 𝐷 ) ∈ V |
8 |
7
|
cnvex |
⊢ ◡ ( pmSgn ‘ 𝐷 ) ∈ V |
9 |
8
|
imaex |
⊢ ( ◡ ( pmSgn ‘ 𝐷 ) “ { 1 } ) ∈ V |
10 |
5 6 9
|
fvmpt |
⊢ ( 𝐷 ∈ V → ( pmEven ‘ 𝐷 ) = ( ◡ ( pmSgn ‘ 𝐷 ) “ { 1 } ) ) |
11 |
2 10
|
syl |
⊢ ( 𝐷 ∈ 𝑉 → ( pmEven ‘ 𝐷 ) = ( ◡ ( pmSgn ‘ 𝐷 ) “ { 1 } ) ) |
12 |
1 11
|
syl5eq |
⊢ ( 𝐷 ∈ 𝑉 → 𝐴 = ( ◡ ( pmSgn ‘ 𝐷 ) “ { 1 } ) ) |