Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 122662
0 votes
0 answers
166 views

Infinity new equilateral triangles in one configuration of triangle plane

You can check the conjecture above hold true for $n=1,\cdots ,3000$ in here the geogebra applet Some new equilateral triangles I discovered recently in here: SOME NEW EQUILATERAL TRIANGLES IN A … PLANE GEOMETRY Some Equilateral Triangles Perspective to the Reference Triangle ABC …
Đào Thanh Oai's user avatar
1 vote

An new equilateral triangle related to the Morley triangle

His paper Equilateral chordal triangles. …
Đào Thanh Oai's user avatar
2 votes
1 answer
371 views

Yiu's equilateral triangle-triplet points

In more than 2300 years since Euclid's Elements appear, there were only two equilateral triangles become famous: The Morely equilateral triangle and the Napoleon equilateral triangle. …
Đào Thanh Oai's user avatar
3 votes
0 answers
886 views

A generalization of the Sawayama-Thebault theorem

1. Introduction The Sawayama-Thebault theorem is one of the best nice theorem in plane geometry. The theorem has a long history. It was published in AMM in 1938 the first solution appeared in 1973 wi …
Đào Thanh Oai's user avatar
3 votes
0 answers
231 views

Are these points known? [closed]

Let $ABC$ be a triangle and $P$ be a point on the plane, $PA$, $PB$, $PC$ meet $BC$, $CA$, $AB$ at $A'$, $B'$, $C'$ respectively. From my construction by GeoGebra, I found two special points as follow …
Đào Thanh Oai's user avatar
3 votes
1 answer
503 views

An new equilateral triangle related to the Morley triangle

Two triangles $A_1B_1C_1$ and $ABC$ are perspective. 3. The triangle $A_1B_1C_1$ and the Morley triangle are homothetic. … Some new equilateral triangles I discovered recently in here: SOME NEW EQUILATERAL TRIANGLES IN A PLANE GEOMETRY Some Equilateral Triangles Perspective to the Reference Triangle ABC …
Đào Thanh Oai's user avatar
1 vote
0 answers
202 views

Some Problems On Apollonian Gasket

Since 2013, I found Some problems on Apollonian Gasket as following. These problem also is higher level of Eppstein Point. I am looking for a proof of one of these problems: Let three $(A)$, $(B)$, $ …
Đào Thanh Oai's user avatar
3 votes
1 answer
138 views

Triangle centers formed a rectangle associated with a convex cyclic quadrilateral

Similarly Japanese theorem for cyclic quadrilaterals, Napoleon theorem, Thébault's theorem, I found a result as follows and I am looking for a proof that: Let $ABCD$ be a convex cyclic quadrilateral. …
Đào Thanh Oai's user avatar
15 votes
2 answers
1k views

Do two new special points in any triangle exist?

There are some special points in any triangle, as Fermat point, symmedian point, incenter, Morley center, et cetera. Let $P$ be a point on the plane, $PA$, $PB$, $PC$ meet $BC$, $CA$, $AB$ at …
Đào Thanh Oai's user avatar
3 votes
1 answer
159 views

Inequality in a triangle associated with Golden ratio

Let $ABC$ be arbitrary triangle, $D$, $E$, $F$ are the midpoints of $BC$, $CA$, $AB$ respectively. Define points, segments in the figure below. I am looking for a proof that: $$DE+EF+FD \le (DG+DH+E …
Đào Thanh Oai's user avatar
4 votes
0 answers
372 views

Two triangles have the same centroid theorem

Let $\triangle ABC$ and $\triangle A'B'C'$ be two triangles. …
Đào Thanh Oai's user avatar
11 votes
3 answers
704 views

An open triangle problem in plane geometry

Some years ago, I asked some 'famous' people in an advanced Plane Geometry forum about the following: Let $ABC$ be arbitrary triangle, how can one construct a point $P$ in the plane such that $P$ is …
Đào Thanh Oai's user avatar