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Description: The scalar field of a subcomplex pre-Hilbert space is closed under square roots of nonnegative reals. (Contributed by Mario Carneiro, 8-Oct-2015)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | cphsca.f | |- F = ( Scalar ` W ) |
|
| cphsca.k | |- K = ( Base ` F ) |
||
| Assertion | cphsqrtcl | |- ( ( W e. CPreHil /\ ( A e. K /\ A e. RR /\ 0 <_ A ) ) -> ( sqrt ` A ) e. K ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | cphsca.f | |- F = ( Scalar ` W ) |
|
| 2 | cphsca.k | |- K = ( Base ` F ) |
|
| 3 | sqrtf | |- sqrt : CC --> CC |
|
| 4 | ffn | |- ( sqrt : CC --> CC -> sqrt Fn CC ) |
|
| 5 | 3 4 | ax-mp | |- sqrt Fn CC |
| 6 | inss2 | |- ( K i^i ( 0 [,) +oo ) ) C_ ( 0 [,) +oo ) |
|
| 7 | rge0ssre | |- ( 0 [,) +oo ) C_ RR |
|
| 8 | ax-resscn | |- RR C_ CC |
|
| 9 | 7 8 | sstri | |- ( 0 [,) +oo ) C_ CC |
| 10 | 6 9 | sstri | |- ( K i^i ( 0 [,) +oo ) ) C_ CC |
| 11 | simp1 | |- ( ( A e. K /\ A e. RR /\ 0 <_ A ) -> A e. K ) |
|
| 12 | elrege0 | |- ( A e. ( 0 [,) +oo ) <-> ( A e. RR /\ 0 <_ A ) ) |
|
| 13 | 12 | biimpri | |- ( ( A e. RR /\ 0 <_ A ) -> A e. ( 0 [,) +oo ) ) |
| 14 | 13 | 3adant1 | |- ( ( A e. K /\ A e. RR /\ 0 <_ A ) -> A e. ( 0 [,) +oo ) ) |
| 15 | 11 14 | elind | |- ( ( A e. K /\ A e. RR /\ 0 <_ A ) -> A e. ( K i^i ( 0 [,) +oo ) ) ) |
| 16 | fnfvima | |- ( ( sqrt Fn CC /\ ( K i^i ( 0 [,) +oo ) ) C_ CC /\ A e. ( K i^i ( 0 [,) +oo ) ) ) -> ( sqrt ` A ) e. ( sqrt " ( K i^i ( 0 [,) +oo ) ) ) ) |
|
| 17 | 5 10 15 16 | mp3an12i | |- ( ( A e. K /\ A e. RR /\ 0 <_ A ) -> ( sqrt ` A ) e. ( sqrt " ( K i^i ( 0 [,) +oo ) ) ) ) |
| 18 | eqid | |- ( Base ` W ) = ( Base ` W ) |
|
| 19 | eqid | |- ( .i ` W ) = ( .i ` W ) |
|
| 20 | eqid | |- ( norm ` W ) = ( norm ` W ) |
|
| 21 | 18 19 20 1 2 | iscph | |- ( W e. CPreHil <-> ( ( W e. PreHil /\ W e. NrmMod /\ F = ( CCfld |`s K ) ) /\ ( sqrt " ( K i^i ( 0 [,) +oo ) ) ) C_ K /\ ( norm ` W ) = ( x e. ( Base ` W ) |-> ( sqrt ` ( x ( .i ` W ) x ) ) ) ) ) |
| 22 | 21 | simp2bi | |- ( W e. CPreHil -> ( sqrt " ( K i^i ( 0 [,) +oo ) ) ) C_ K ) |
| 23 | 22 | sselda | |- ( ( W e. CPreHil /\ ( sqrt ` A ) e. ( sqrt " ( K i^i ( 0 [,) +oo ) ) ) ) -> ( sqrt ` A ) e. K ) |
| 24 | 17 23 | sylan2 | |- ( ( W e. CPreHil /\ ( A e. K /\ A e. RR /\ 0 <_ A ) ) -> ( sqrt ` A ) e. K ) |