Theorem abvfge0

Description: An absolute value is a function from the ring to the nonnegative real numbers. (Contributed by Mario Carneiro, 8-Sep-2014)

	Ref	Expression
Hypotheses	abvf.a	|- A = ( AbsVal ` R )
	abvf.b	|- B = ( Base ` R )
Assertion	abvfge0	|- ( F e. A -> F : B --> ( 0 [,) +oo ) )

Proof

Step	Hyp	Ref	Expression
1		abvf.a	|- A = ( AbsVal ` R )
2		abvf.b	|- B = ( Base ` R )
3	1	abvrcl	|- ( F e. A -> R e. Ring )
4		eqid	|- ( +g ` R ) = ( +g ` R )
5		eqid	|- ( .r ` R ) = ( .r ` R )
6		eqid	|- ( 0g ` R ) = ( 0g ` R )
7	1 2 4 5 6	isabv	|- ( R e. Ring -> ( F e. A <-> ( F : B --> ( 0 [,) +oo ) /\ A. x e. B ( ( ( F ` x ) = 0 <-> x = ( 0g ` R ) ) /\ A. y e. B ( ( F ` ( x ( .r ` R ) y ) ) = ( ( F ` x ) x. ( F ` y ) ) /\ ( F ` ( x ( +g ` R ) y ) ) <_ ( ( F ` x ) + ( F ` y ) ) ) ) ) ) )
8	3 7	syl	|- ( F e. A -> ( F e. A <-> ( F : B --> ( 0 [,) +oo ) /\ A. x e. B ( ( ( F ` x ) = 0 <-> x = ( 0g ` R ) ) /\ A. y e. B ( ( F ` ( x ( .r ` R ) y ) ) = ( ( F ` x ) x. ( F ` y ) ) /\ ( F ` ( x ( +g ` R ) y ) ) <_ ( ( F ` x ) + ( F ` y ) ) ) ) ) ) )
9	8	ibi	|- ( F e. A -> ( F : B --> ( 0 [,) +oo ) /\ A. x e. B ( ( ( F ` x ) = 0 <-> x = ( 0g ` R ) ) /\ A. y e. B ( ( F ` ( x ( .r ` R ) y ) ) = ( ( F ` x ) x. ( F ` y ) ) /\ ( F ` ( x ( +g ` R ) y ) ) <_ ( ( F ` x ) + ( F ` y ) ) ) ) ) )
10	9	simpld	|- ( F e. A -> F : B --> ( 0 [,) +oo ) )