Talk:Sum of angles of a triangle

Reference to equivalence of parallel postulate and Pythagoras' theorem

The Pruss book cited (of which I am the author) is not a mathematics book. It would be better to have a citation to a mathematics book that has a proof of the claim. Pruss (talk) 17:50, 11 November 2010 (UTC)

It would be nice to see here why these propositions are true. — Preceding unsigned comment added by 213.185.243.153 (talk) 23:05, 26 January 2012 (UTC)

November 2013 edits

I've made a couple of changes that need more of an explanation than can fit in an edit summary.

1. In the equidistant postulate statement a parenthetical definition was given. I wasn't happy with the way this was phrased, so I changed it. Apparently my change was a bit awkward and it got changed to something which missed the point that I was trying to make (that is, I was looking for a succinct way to say that it doesn't matter which point on either line you pick, its distance to the other line is the same). Perhaps it is better to say less than more in this instance, so my latest edit is intended to simplify.
2. In the section on hyperbolic geometry there was a parenthetical remark about why the equidistant postulate fails. While this was ok, it used the word parallel (in quotes) and since parallel in this context can have several meanings I thought it would be better to replace the statement by something which avoided that possible confusion.
3. In the section on exterior angles I had inserted the phrase "can be unambiguously defined" in reference to interior angles. I did this because in elliptic geometry three noncollinear points do not determine a unique triangle and you must redefine what a triangle is before you can talk about interior angles–but once this is done everything goes as before. Perhaps I am being a bit too picky for the level at which this article is currently written. Bill Cherowitzo (talk) 18:03, 20 November 2013 (UTC)

I have no objections about 1. and 2. As for 3. yes, there are clauses related to interior angles for spherical geometry (as for any non-convex polygon, but only in the elliptic case a triangle can be non-convex), so I’d not say that they are “unambiguously defined” without an explication. BTW, the non-convex case makes exterior angles negative – IMHO we have either explain this case or explicitly avoid considering it. Incnis Mrsi (talk) 16:54, 21 November 2013 (UTC)

Requested move 9 May 2017

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: No consensus apparent for a move. Many folks voiced option 3 (current) to be fine — Andy W. (talk) 05:55, 18 May 2017 (UTC)

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Sum of angles of a triangle → ? – The current title is not very concise and sounds somewhat unencyclopedic, so I am proposing three options:

1. Angle sum of a triangle, which appears to be more common and is more concise;
2. Triangle postulate, which is the technical name of this topic, and is how Wolfram MathWorld refers to it;
3. Sum of angles of a triangle, the current name.

Please indicate which you prefer. Thanks, Laurdecl ^talk 11:47, 9 May 2017 (UTC)

• Option 1, maybe 2 as nom. Laurdecl ^talk 11:47, 9 May 2017 (UTC)
• Nothing wrong with 3, which we have now. Anthony Appleyard (talk) 18:26, 9 May 2017 (UTC)
• Option 3. The three letter difference with the first option does not seem to be worth the effort. I strongly oppose option 2 as it is modern jargon that does not inform the reader of the content.--Bill Cherowitzo (talk) 19:07, 9 May 2017 (UTC)

There isn't really any effort involved. I thought it would be better to have less "of"s in the title. Laurdecl ^talk 10:24, 10 May 2017 (UTC)

Sum of angles in a triangle? Lugnuts ^{Fire Walk with Me} 17:34, 10 May 2017 (UTC)

• Option 3 – it's just fine and quite idiomatic, as evidenced by thousands of Ghits for that exact phrase; "Sum of angles in a triangle" is about equally fine, but then WP:TITLECHANGES. We don't have to be concise at all costs, particularly in descriptive titles; "angle sum of a triangle" sounds headlinese to me, and "triangle postulate" is way too technical. No such user (talk) 12:09, 11 May 2017 (UTC)

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The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

Quadrilaterals

What is a sum of triangle? Sum of triangle is 180 Because of is half of triangle is formed by the 90° and the full triangle of is 180° That means sum of triangle is 180° — Preceding unsigned comment added by 103.234.240.141 (talk) 02:38, 9 July 2024 (UTC)

The exterior angles (a.k.a. turning angles) of any simple polygon always sum to a full turn (360°). Because each interior angle is the supplement of the corresponding exterior angle (the two sum to a straight angle, 180°), it is not too hard to figure out a formula for the sum of the interior angles in any simple polygon based on the number of sides: It must be n×180° − 360°. –jacobolus (t) 17:48, 10 July 2024 (UTC)