Prove or disprove the non colinearity of three points












1












$begingroup$


Prove or disprove: Let $ABCD$ be a quadrilateral in Pasch Geometry for which the following holds $ABcap CD={E}$, $ACcap BD={F}$ and $ADcap BC={G}$. Then the points $E,F,G$ are not collinear.



I tried to prove by contradiction defining a graph on set ${A,B,C,D}$ with edge between two points if they lie on different sides of the line $EFG$ but couldn't arrive to a contradiction. Maybe there is a counterexample in Poincaré Geometry.










share|cite|improve this question









$endgroup$








  • 2




    $begingroup$
    The same question on MathOverflow: Prove or disprove the non colinearity of three points. For some advice on corss-posting see this answer on meta and other questions tagged cross-posting.
    $endgroup$
    – Martin Sleziak
    Dec 7 '18 at 6:59
















1












$begingroup$


Prove or disprove: Let $ABCD$ be a quadrilateral in Pasch Geometry for which the following holds $ABcap CD={E}$, $ACcap BD={F}$ and $ADcap BC={G}$. Then the points $E,F,G$ are not collinear.



I tried to prove by contradiction defining a graph on set ${A,B,C,D}$ with edge between two points if they lie on different sides of the line $EFG$ but couldn't arrive to a contradiction. Maybe there is a counterexample in Poincaré Geometry.










share|cite|improve this question









$endgroup$








  • 2




    $begingroup$
    The same question on MathOverflow: Prove or disprove the non colinearity of three points. For some advice on corss-posting see this answer on meta and other questions tagged cross-posting.
    $endgroup$
    – Martin Sleziak
    Dec 7 '18 at 6:59














1












1








1





$begingroup$


Prove or disprove: Let $ABCD$ be a quadrilateral in Pasch Geometry for which the following holds $ABcap CD={E}$, $ACcap BD={F}$ and $ADcap BC={G}$. Then the points $E,F,G$ are not collinear.



I tried to prove by contradiction defining a graph on set ${A,B,C,D}$ with edge between two points if they lie on different sides of the line $EFG$ but couldn't arrive to a contradiction. Maybe there is a counterexample in Poincaré Geometry.










share|cite|improve this question









$endgroup$




Prove or disprove: Let $ABCD$ be a quadrilateral in Pasch Geometry for which the following holds $ABcap CD={E}$, $ACcap BD={F}$ and $ADcap BC={G}$. Then the points $E,F,G$ are not collinear.



I tried to prove by contradiction defining a graph on set ${A,B,C,D}$ with edge between two points if they lie on different sides of the line $EFG$ but couldn't arrive to a contradiction. Maybe there is a counterexample in Poincaré Geometry.







geometry






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Dec 6 '18 at 21:31









user183294user183294

353




353








  • 2




    $begingroup$
    The same question on MathOverflow: Prove or disprove the non colinearity of three points. For some advice on corss-posting see this answer on meta and other questions tagged cross-posting.
    $endgroup$
    – Martin Sleziak
    Dec 7 '18 at 6:59














  • 2




    $begingroup$
    The same question on MathOverflow: Prove or disprove the non colinearity of three points. For some advice on corss-posting see this answer on meta and other questions tagged cross-posting.
    $endgroup$
    – Martin Sleziak
    Dec 7 '18 at 6:59








2




2




$begingroup$
The same question on MathOverflow: Prove or disprove the non colinearity of three points. For some advice on corss-posting see this answer on meta and other questions tagged cross-posting.
$endgroup$
– Martin Sleziak
Dec 7 '18 at 6:59




$begingroup$
The same question on MathOverflow: Prove or disprove the non colinearity of three points. For some advice on corss-posting see this answer on meta and other questions tagged cross-posting.
$endgroup$
– Martin Sleziak
Dec 7 '18 at 6:59










0






active

oldest

votes











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3029074%2fprove-or-disprove-the-non-colinearity-of-three-points%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























0






active

oldest

votes








0






active

oldest

votes









active

oldest

votes






active

oldest

votes
















draft saved

draft discarded




















































Thanks for contributing an answer to Mathematics Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3029074%2fprove-or-disprove-the-non-colinearity-of-three-points%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Plaza Victoria

Brian Clough

Cáceres