Metamath Proof Explorer


Theorem blcntr

Description: A ball contains its center. (Contributed by NM, 2-Sep-2006) (Revised by Mario Carneiro, 12-Nov-2013)

Ref Expression
Assertion blcntr D ∞Met X P X R + P P ball D R

Proof

Step Hyp Ref Expression
1 rpxr R + R *
2 rpgt0 R + 0 < R
3 1 2 jca R + R * 0 < R
4 xblcntr D ∞Met X P X R * 0 < R P P ball D R
5 3 4 syl3an3 D ∞Met X P X R + P P ball D R