New posts in triangles

Does $\triangle ABC$ exist such that $\triangle ABC \sim \triangle DEF$, with $D, E, F$ being the incentre, centroid, orthocentre of $\triangle ABC$?

geometry euclidean-geometry triangles

Partial derivatives on area of a triangle

analysis multivariable-calculus triangles

$\frac1{12}(\sin^2A+\sin^2B+\sin^2C)\leq \sin^2\frac12B\sin^2\frac12C+\sin^2\frac12C\sin^2\frac12A+\sin^2\frac12A\sin^2\frac12B$ for $A+B+C=180^\circ$

algebra-precalculus trigonometry inequality triangles

Is there an equidissection of a unit square involving irrational coordinates?

geometry triangles combinatorial-geometry

For which $n$ are there primitive Pythagorean triples with legs of lengths $a$ and $a+n$?

elementary-number-theory diophantine-equations triangles pythagorean-triples

Formula for distance between Incenter and Orthocenter.

geometry euclidean-geometry triangles

A Math Olympiad question regarding Geometry

geometry contest-math triangles

How to find coordinates of 3rd vertex of a right angled triangle when everything else is known?

geometry trigonometry triangles coordinate-systems solid-angle

If $a$, $b$, and $c$ are sides of a triangle, then $\frac{a}{b+c}+\frac{b}{c+a}+\frac{c}{a+b}<2$.

inequality contest-math euclidean-geometry triangles geometric-inequalities

If $a+b+c$ divides the product $abc$, then is $(a,b,c)$ a Pythagorean Triple?

geometry proof-writing triangles conjectures pythagorean-triples

A flower in a hexagon

geometry triangles area

Another conjecture about a circle intrinsically bound to any triangle

geometry euclidean-geometry triangles

Is there a name for the recursive incenter of the contact triangle?

geometry euclidean-geometry triangles recursion

Five Similar Triangles from 4-5-6

geometry triangles recreational-mathematics puzzle

Determine if projection of 3D point onto plane is within a triangle

geometry triangles 3d

Find the perimeter of a polygon $ABCDEF$

geometry triangles circles polygons

Prove that :$[BCA']^2+[CAB']^2+[ABC']^2=[ABC]^2$, where [•] denote the area.

geometry triangles

BdMO 2016 National Secondary Problem 3.

geometry contest-math triangles angle

Can area be irrational?

analytic-geometry triangles coordinate-systems

Is an equilateral triangle the same as an equiangular triangle, in any geometry?

geometry triangles hyperbolic-geometry spherical-geometry