# Paranormal implies weakly normal

From Groupprops

Revision as of 23:19, 11 February 2009 by Vipul (talk | contribs) (New page: {{subgroup property implication| stronger = paranormal subgroup| weaker = weakly normal subgroup}} ==Statement== ===Verbal statement=== A paranormal subgroup of a group must be a [[...)

This article gives the statement and possibly, proof, of an implication relation between two subgroup properties. That is, it states that every subgroup satisfying the first subgroup property (i.e., paranormal subgroup) must also satisfy the second subgroup property (i.e., weakly normal subgroup)

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## Statement

### Verbal statement

A paranormal subgroup of a group must be a weakly normal subgroup.

### Statement with symbols

Suppose is a subgroup of such that is contranormal in for any . Then, if , we have .

## Related facts

## Proof

**Given**: A group . A subgroup such that is contranormal in for any .

**To prove**: If , then .

**Proof**: Since , we have . In particular, is normal in . On the other hand, by paranormality, we have that the normal closure of in is . This forces , so .