{ localUrl: '../page/dihedral_group.html', arbitalUrl: 'https://arbital.com/p/dihedral_group', rawJsonUrl: '../raw/4cy.json', likeableId: '2717', likeableType: 'page', myLikeValue: '0', likeCount: '1', dislikeCount: '0', likeScore: '1', individualLikes: [ 'EricBruylant' ], pageId: 'dihedral_group', edit: '3', editSummary: '', prevEdit: '2', currentEdit: '3', wasPublished: 'true', type: 'wiki', title: 'Dihedral group', clickbait: 'The dihedral groups are natural examples of groups, arising from the symmetries of regular polygons.', textLength: '1350', alias: 'dihedral_group', externalUrl: '', sortChildrenBy: 'likes', hasVote: 'false', voteType: '', votesAnonymous: 'false', editCreatorId: 'PatrickStevens', editCreatedAt: '2016-06-16 20:38:00', pageCreatorId: 'PatrickStevens', pageCreatedAt: '2016-06-15 14:53:04', seeDomainId: '0', editDomainId: 'AlexeiAndreev', submitToDomainId: '0', isAutosave: 'false', isSnapshot: 'false', isLiveEdit: 'true', isMinorEdit: 'false', indirectTeacher: 'false', todoCount: '4', isEditorComment: 'false', isApprovedComment: 'true', isResolved: 'false', snapshotText: '', anchorContext: '', anchorText: '', anchorOffset: '0', mergedInto: '', isDeleted: 'false', viewCount: '38', text: 'The dihedral group $D_{2n}$ is the group of symmetries of the $n$-vertex [-regular_polygon].\n\n# Presentation\nThe dihedral groups have very simple [group_presentation presentations]: $$D_{2n} \\cong \\langle a, b \\mid a^n, b^2, b a b^{-1} = a^{-1} \\rangle$$\nThe element $a$ represents a rotation, and the element $b$ represents a reflection in any fixed axis.\n[todo: picture]\n\n# Properties\n\n- The dihedral groups $D_{2n}$ are all non-abelian for $n > 2$. ([4d0 Proof.])\n- The dihedral group $D_{2n}$ is a [-subgroup] of the [-497] $S_n$, generated by the elements $a = (123 \\dots n)$ and $b = (2, n)(3, n-1) \\dots (\\frac{n}{2}+1, \\frac{n}{2}+3)$ if $n$ is even, $b = (2, n)(3, n-1)\\dots(\\frac{n-1}{2}, \\frac{n+1}{2})$ if $n$ is odd.\n\n# Examples\n\n## $D_6$, the group of symmetries of the triangle\n\n[todo: diagram]\n[todo: list the elements and Cayley table]\n\n# Infinite dihedral group\n\nThe infinite dihedral group has presentation $\\langle a, b \\mid b^2, b a b^{-1} = a^{-1} \\rangle$.\nIt is the "infinite-sided" version of the finite $D_{2n}$.\n\nWe may view the infinite dihedral group as being the subgroup of the group of [homeomorphism homeomorphisms] of $\\mathbb{R}^2$ generated by a reflection in the line $x=0$ and a translation to the right by one unit.\nThe translation is playing the role of a rotation in the finite $D_{2n}$.\n\n[todo: this section]', metaText: '', isTextLoaded: 'true', isSubscribedToDiscussion: 'false', isSubscribedToUser: 'false', isSubscribedAsMaintainer: 'false', discussionSubscriberCount: '1', maintainerCount: '1', userSubscriberCount: '0', lastVisit: '', hasDraft: 'false', votes: [], voteSummary: 'null', muVoteSummary: '0', voteScaling: '0', currentUserVote: '-2', voteCount: '0', lockedVoteType: '', maxEditEver: '0', redLinkCount: '0', lockedBy: '', lockedUntil: '', nextPageId: '', prevPageId: '', usedAsMastery: 'false', proposalEditNum: '0', permissions: { edit: { has: 'false', reason: 'You don't have domain permission to edit this page' }, proposeEdit: { has: 'true', reason: '' }, delete: { has: 'false', reason: 'You don't have domain permission to delete this page' }, comment: { has: 'false', reason: 'You can't comment in this domain because you are not a member' }, proposeComment: { has: 'true', reason: '' } }, summaries: {}, creatorIds: [ 'PatrickStevens' ], childIds: [ 'dihedral_groups_are_non_abelian' ], parentIds: [ 'group_mathematics' ], commentIds: [], questionIds: [], tagIds: [ 'definition_meta_tag', 'stub_meta_tag' ], relatedIds: [], markIds: [], explanations: [], learnMore: [], requirements: [], subjects: [], lenses: [], lensParentId: '', pathPages: [], learnMoreTaughtMap: {}, learnMoreCoveredMap: {}, learnMoreRequiredMap: {}, editHistory: {}, domainSubmissions: {}, answers: [], answerCount: '0', commentCount: '0', newCommentCount: '0', linkedMarkCount: '0', changeLogs: [ { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '13380', pageId: 'dihedral_group', userId: 'PatrickStevens', edit: '3', type: 'newEdit', createdAt: '2016-06-16 20:38:00', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '13068', pageId: 'dihedral_group', userId: 'PatrickStevens', edit: '2', type: 'newEdit', createdAt: '2016-06-15 15:05:39', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '13065', pageId: 'dihedral_group', userId: 'PatrickStevens', edit: '1', type: 'newChild', createdAt: '2016-06-15 14:59:08', auxPageId: 'dihedral_groups_are_non_abelian', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '13062', pageId: 'dihedral_group', userId: 'PatrickStevens', edit: '1', type: 'newEdit', createdAt: '2016-06-15 14:53:04', auxPageId: '', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '13058', pageId: 'dihedral_group', userId: 'PatrickStevens', edit: '1', type: 'newTag', createdAt: '2016-06-15 14:51:56', auxPageId: 'stub_meta_tag', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '13057', pageId: 'dihedral_group', userId: 'PatrickStevens', edit: '1', type: 'newTag', createdAt: '2016-06-15 14:50:35', auxPageId: 'definition_meta_tag', oldSettingsValue: '', newSettingsValue: '' }, { likeableId: '0', likeableType: 'changeLog', myLikeValue: '0', likeCount: '0', dislikeCount: '0', likeScore: '0', individualLikes: [], id: '13056', pageId: 'dihedral_group', userId: 'PatrickStevens', edit: '1', type: 'newParent', createdAt: '2016-06-15 14:50:30', auxPageId: 'group_mathematics', oldSettingsValue: '', newSettingsValue: '' } ], feedSubmissions: [], searchStrings: {}, hasChildren: 'true', hasParents: 'true', redAliases: {}, improvementTagIds: [], nonMetaTagIds: [], todos: [], slowDownMap: 'null', speedUpMap: 'null', arcPageIds: 'null', contentRequests: {} }