Theorem sqrtsqi

Description: Square root of square. (Contributed by NM, 11-Aug-1999)

	Ref	Expression
Hypothesis	sqrtthi.1	|- A e. RR
Assertion	sqrtsqi	|- ( 0 <_ A -> ( sqrt ` ( A ^ 2 ) ) = A )

Proof

Step	Hyp	Ref	Expression
1		sqrtthi.1	|- A e. RR
2		sqrtsq	|- ( ( A e. RR /\ 0 <_ A ) -> ( sqrt ` ( A ^ 2 ) ) = A )
3	1 2	mpan	|- ( 0 <_ A -> ( sqrt ` ( A ^ 2 ) ) = A )