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Talk:Quadrilateral

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overly detailed proof by cutting out some steps or expand the details of a concise proof sketch, consolidate the proof of a lemma into the main proof, or splice two slightly different proofs together from different sources. We can make up our own examples instead of exactly quoting examples found in a textbook. We can e.g. take a statement written in terms of separate coordinate and rewrite it in terms of vector identities. That type of thing. It's still important to have sources for claims made though, instead of doing
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I'm glad you included a source this time, even if it was the not particularly great source I found for you here. I am nonetheless not impressed with your edit summary of "rv unconstructive", which continues to be gratuitously aggressive. You might consider apologizing to DVdm for your comments, which
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Perhaps we could compromise by replacing two "No"s with a note that, although the most general trapezoids and isosceles trapezoids do not have perpendicular diagonals, there is an infinite number of (non-similar) trapezoids and isosceles trapezoids that do have perpendicular diagonals and are not any
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are the diagonals of the quadrilateral.) if you hunted around in old geometry books. In general, hunting around in books, finding the material that seems most relevant and important, and then adding it with a cited source is a much better strategy for improving Knowledge than working out identities
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is not that we can include any provable statement, so long as the proof isn't too hard, but rather that we can make statements whose basic claims are established by reliable sources but phrased in ways that aren't necessarily identical. For example, in an article about a theorem, we can simplify an
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I editted them.Could you check if it is right?The area of the Varignon parallelogram equals half the area of the original quadrilateral. This is true in convex, concave and crossed quadrilaterals provided the area of the latter is defined to be the difference of the areas of the two triangles it is
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Shouldn't the isosceles trapezoid be between the trapezoid and parallelogram instead of between the trapezoid and the rectangle to be fully inclusive? An isosceles trapezoid has one+ pair of parallel sides and one+ pair of congruent sides, so wouldn't that all be inherited by a parallelogram?
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Indeed. Even tangential quadrilaterals which are also right-angled trapezia. (But not every tangential quadrilateral is a trapezium.) You're welcome to extend the diagram to add the new categories, though I think "cyclic right-angled trapezium" might be a bit obscure...
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In general, hunting around in books, finding the material that seems most relevant and important, and then adding it with a cited source is a much better strategy for improving Knowledge than working out identities for yourself on scrap
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I don't have a clear sense of what's most helpful. Perhaps every "no" has exceptions and could be explained, like "no, becomes a square", etc. With "no, in general" if there's no special name for the special cases!
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The cell for whether an isosceles trapezoid has perpendicular diagonals says "Not in general", but the cell for whether a kite has congruent diagonals, which this same phrase fits equally, says "No". Any thoughts??
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Don't we? When I search Google for the definition of trilateral one of the results is a triangle. Same for trigon. Also, triangle is parallel to a third word for a quadrilateral or tetragon, namely "quadrangle".
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talk about these special case, probably because there's no new symmetry involved. If the articles note the cases, then perhaps a mark in the table could note that with wlink referencing why its noteworthy.
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To answer my own question, an isosceles trapezoid also has congruent diagonals, which a parallelogram does not, so not all properties are inherited. Symmetry is also not inherited. --
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I'm also fairly certain you would be able to find several sources for this claim (For anyone reading along without looking at reverted changes, the identity is: The angle
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Is there a reason why we don't use the word quadragon instead of quadrilateral? After all it has the same meaning as hexagon (hex meaning 6) or pentagon (penta meaning 5)
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Because the word of that form that we (rarely) use is instead "tetragon". I don't know what history led to the different choice of root for the number four. —
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Yes, you are correct. (I'd missed seeing that! Apologies to Georgia Guy.) The whole table has issues. Have we made it too complicated with the notes?
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David Eppstein, I have known since I was a child that 'quadrangle' is an alternative name for 'quadrilateral'. Please do not take me for an idiot.
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is to omit the case of convex and concave quadrilateral.)If we check the sign in each case,it is like above.And we have this formura.
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I agree with GG, and changed the "not in general" entry back to "no". Special cases ought to be treated equally. Plus, nothing at
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I think all the other cases are covered by the caveat above the table, but I'll not object if you want to make that adjustment.
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Also, it was explained to you before that sources are not only needed for verification, but also to demonstrate notability. See
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I found in a 1 minute search as used in the proof of "Coolidge's formula". There are many related identities discussed in
135: 74: 1662:{\displaystyle S={\frac {1}{2}}pq\sin(\theta _{1}\pm \theta _{2})={\frac {a|\sin A|(d-cosD)\pm (d-a\cos A)c|\sin D|}{2}}} 858: 256: 190: 65: 2313: 491:) An isosceles trapezoid can have perpendicular diagonals without being anything other than an isosceles trapezoid. 1019:
David Eppstein, I was born and bred in the UK and English is my first language. Please don't ever insult me again.
1899: 1295: 202: 185: 1888:, please stop vandalising the article. A clear explanation of why this formula is correct was given in the edit. 1847: 988:
If you want a language that is designed to be logical and consistent, then English is not for you. You could try
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to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the
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http://web.archive.org/web/20120819055027/http://www.chrisvantienhoven.nl:80/mathematics/encyclopedia.html
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If you have discovered URLs which were erroneously considered dead by the bot, you can report them with
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http://web.archive.org/web/20140514200449/http://www.cimt.plymouth.ac.uk:80/resources/topics/art002.pdf
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If thats the case then why don't we call a triangle a 'trilateral' or a hexagon a 'hexalateral'?
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Just a curious thought more than anything. I am not trying to instigate an edit war or anything.
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on Knowledge. If you would like to participate, please visit the project page, where you can join
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What is a "kite with equal diagonals" called? If the equal diagonals have the same center, its a
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before doing mass systematic removals. This message is updated dynamically through the template
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Ah yes, the "I don't like this editor so I am going to undo all of their edits for no reason".
1454:{\displaystyle \sin \theta _{1}={\frac {a|\sin A|}{q}},\ cos\theta _{1}={\frac {d-a\cos A}{q}}} 834: 764:
http://web.archive.org/web/20110719175018/http://mzone.mweb.co.za/residents/profmd/classify.pdf
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https://en.wikipedia.org/search/?title=Quadrilateral&diff=1072455009&oldid=1072428222
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Again, "hex-" for 6 is a Greek prefix which would not usually be added to a Latin root...
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thanks for the comment. I have added urls for the source, so others can easily verify. -
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If you found an error with any archives or the URLs themselves, you can fix them with
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A kite can have equal diagonals only when it is a named subset of the set of kites.
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Liking or disliking editors has nothing to do with any of this. This is about
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There could be tangential quadrilaterals which are also trapezoids. No? --
217: 2228: 2235: 2221: 570:, but otherwise, it's still just a kite to all the terminology I know. 2291: 2262: 2245: 2208: 2051: 2008: 1982: 1973: 1935: 1919: 1892: 1873: 1127: 1088: 1050: 1005: 982: 948: 907: 863: 702: 652: 621: 579: 553: 516: 474: 450: 429: 414: 989: 567: 2167:{\displaystyle \cos \theta ={\frac {a^{2}+c^{2}-b^{2}-d^{2}}{2pq}},} 1265:{\displaystyle S={\frac {a\sin A(d-c\cos D)+(d-a\cos A)c\sin D}{2}}} 1880:
The angle between diagonals in terms of the sides and diagonals
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http://www.chrisvantienhoven.nl/mathematics/encyclopedia.html
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When you have finished reviewing my changes, please set the
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I disagree because of the caveat I placed above the table.
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Sorry,I misunderstanded a part.It was right about the part.
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template there, but removal also seems fine. The point of
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http://www.cimt.plymouth.ac.uk/resources/topics/art002.pdf
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for additional information. I made the following changes:
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And then it says what routine calculations are. Read it.
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So quadragon (quad meaning 4) should have some sense.
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Routine calculations do not count as original research
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http://mzone.mweb.co.za/residents/profmd/classify.pdf
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is Latin and should use the Latin root for 4, hence
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If the word 923:is Greek and should use the Greek root, hence 796:This message was posted before February 2018. 993: 174: 8: 868: 1340:According to sine law and first cosine law, 1165:And furthermore,we have this area formura. 1095: 1057: 1020: 968: 877: 270: 2179: 2141: 2128: 2115: 2102: 2095: 2081: 2061: 1819: 1728: 1718: 1712: 1702: 1694: 1674: 1648: 1634: 1575: 1561: 1555: 1543: 1530: 1501: 1493: 1472: 1466: 1424: 1415: 1386: 1372: 1366: 1357: 1345: 1305: 1297: 1277: 1178: 1170: 726:I have just modified 3 external links on 1955:Talk:Regular_polygon#Less_than_pi,_sure. 2341:Knowledge vital articles in Mathematics 1898:HTML comments are not considered to be 272: 231: 2300: 2238:, which discuss related identities. – 1928: 869:Why don't we use the term 'quadragon'? 2356:C-Class vital articles in Mathematics 785:to let others know (documentation at 7: 1999:about that on your user talk page - 318:This article is within the scope of 1152:240D:1E:309:5F00:77B:76BC:5AAE:498E 261:It is of interest to the following 23:for discussing improvements to the 2366:High-priority mathematics articles 14: 2255:were insulting and out of line. – 1488:.According to angle sum identity, 730:. Please take a moment to review 338:Knowledge:WikiProject Mathematics 2336:Knowledge level-4 vital articles 1991:. You might also have a look at 1927:, which you are citing, states: 1292:can make between extended lines, 341:Template:WikiProject Mathematics 305: 295: 274: 241: 232: 201: 45:Click here to start a new topic. 358:This article has been rated as 2346:C-Class level-4 vital articles 2314:22:56, 14 September 2024 (UTC) 2292:19:04, 14 September 2024 (UTC) 2263:18:33, 14 September 2024 (UTC) 2246:18:30, 13 September 2024 (UTC) 2209:18:14, 13 September 2024 (UTC) 2201:for yourself on scrap paper. – 2052:18:05, 13 September 2024 (UTC) 2009:10:03, 13 September 2024 (UTC) 1983:09:48, 13 September 2024 (UTC) 1974:08:26, 13 September 2024 (UTC) 1936:08:17, 13 September 2024 (UTC) 1920:08:15, 13 September 2024 (UTC) 1893:08:13, 13 September 2024 (UTC) 1816: 1785: 1764: 1761: 1740: 1737: 1649: 1635: 1628: 1607: 1601: 1580: 1576: 1562: 1549: 1523: 1387: 1373: 1241: 1220: 1214: 1193: 1072:23:36, 30 September 2016 (UTC) 1: 1160:03:24, 20 February 2022 (UTC) 1110:22:53, 16 November 2016 (UTC) 1035:22:49, 16 November 2016 (UTC) 949:03:07, 3 September 2016 (UTC) 908:15:57, 2 September 2016 (UTC) 892:12:48, 2 September 2016 (UTC) 332:and see a list of open tasks. 42:Put new text under old text. 2361:C-Class mathematics articles 1461:Similary,we can proof about 1006:20:05, 11 October 2016 (UTC) 983:18:54, 11 October 2016 (UTC) 528:other named quadrilateral. 1481:{\displaystyle \theta _{2}} 1128:17:36, 8 October 2016 (UTC) 1089:00:01, 1 October 2016 (UTC) 50:New to Knowledge? Welcome! 2382: 1051:20:40, 11 March 2023 (UTC) 827:(last update: 5 June 2024) 723:Hello fellow Wikipedians, 703:22:53, 29 March 2013 (UTC) 653:22:47, 29 March 2013 (UTC) 622:22:34, 29 March 2013 (UTC) 580:22:16, 29 March 2013 (UTC) 554:22:09, 29 March 2013 (UTC) 517:21:26, 29 March 2013 (UTC) 475:21:11, 29 March 2013 (UTC) 451:20:58, 29 March 2013 (UTC) 400:12:55:55, 2005-08-03 (UTC) 383:The classification picture 864:12:11, 21 July 2016 (UTC) 430:04:02, 4 March 2014 (UTC) 415:02:58, 4 March 2014 (UTC) 357: 290: 269: 80:Be welcoming to newcomers 2214:Here's an example source 1874:22:24, 30 May 2022 (UTC) 994:http://jbo.wikipedia.org 391:9 July 2005 16:02 (UTC) 364:project's priority scale 2274:thanks for the source. 2069:{\displaystyle \theta } 1285:{\displaystyle \theta } 1272:I'll show the proof.As 1136:Bretschneider's formula 1135: 719:External links modified 321:WikiProject Mathematics 2331:C-Class vital articles 2194: 2168: 2070: 1831: 1683: 1663: 1482: 1455: 1334: 1286: 1266: 75:avoid personal attacks 2304:This is good advice. 2195: 2169: 2071: 1832: 1684: 1664: 1483: 1456: 1335: 1287: 1267: 248:level-4 vital article 195:Auto-archiving period 100:Neutral point of view 2178: 2080: 2060: 1693: 1682:{\displaystyle \pm } 1673: 1492: 1465: 1344: 1296: 1276: 1169: 808:regular verification 344:mathematics articles 105:No original research 2193:{\displaystyle p,q} 2042:"original research" 1900:wp:reliable sources 939:as the root for 3. 798:After February 2018 777:parameter below to 462:isosceles trapezoid 2222:10.1017/mag.2021.9 2190: 2164: 2066: 1827: 1679: 1659: 1478: 1451: 1330: 1282: 1262: 852:InternetArchiveBot 803:InternetArchiveBot 489:See apology below. 486: 313:Mathematics portal 257:content assessment 86:dispute resolution 47: 2159: 1862:original research 1842:comment added by 1825: 1710: 1657: 1509: 1449: 1401: 1395: 1313: 1260: 1112: 1100:comment added by 1074: 1062:comment added by 1037: 1025:comment added by 985: 973:comment added by 964:triangleometry?'' 927:. In the case of 894: 882:comment added by 828: 490: 484: 378: 377: 374: 373: 370: 369: 226: 225: 66:Assume good faith 43: 2373: 2281: 2273: 2224:. 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