AoPS Academy
[/quote]
, do not answer with "
is a solution" only. Either you post any kind of proof or at least something unexpected (like "
is the smallest solution). Someone that does not see that is a solution of the above without your post is completely wrong here, this is an IMO-level forum.
. Solve the equation: 
be a triangle and let 
be its circumcenter and 
its incenter.
be the radical center of its three mixtilinears and let 
be the isogonal conjugate of .
be the Gergonne point of the triangle .
is parallel with line 
.
be the unit circle in the complex plane. Let 
be the map given by 
. We define 
and 
for 
. The smallest positive integer 
such that 
is called the period of 
. Determine the total number of points in 
of period 
.
)
be a positive integer. Prove that there exist three permutations 
, 
, and 
of 
such that ![\[\left|\sqrt{a_k}+\sqrt{b_k}+\sqrt{c_k}-2\sqrt{N}\right|<2023\]](http://latex.artofproblemsolving.com/9/8/0/98097fb721722b9103ef65d72322956877e262cb.png)
for every 
.
, no matter how its elements are partitioned into two subsets, at least one of the subsets must contain three numbers 
(
is allowed) such that 
. Find the minimal .
and a point , let 
be the cevian triangle of with respect to . Let 
be the orthocenter of , and denote the isotomic conjugate of 
with respect to by 
, respectively. Let the centroid of be 
, and denote the isogonal conjugate of with respect to by 
. Prove that
or in brief
be the circumcenter and the orthocenter of an acute triangle . Prove that the area of one of the triangles 
, 
and 
is equal to the sum of the areas of the other two.
line segments in the plane such that every two segments cross and no three segments meet at a point. Geoff has to choose an endpoint of each segment and place a frog on it facing the other endpoint. Then he will clap his hands 
times. Every time he claps,each frog will immediately jump forward to the next intersection point on its segment. Frogs never change the direction of their jumps. Geoff wishes to place the frogs in such a way that no two of them will ever occupy the same intersection point at the same time. is odd. is even.
such that a positive integer power of 
equals to a positive integer power of 
.
can be written in the form
where 
for some non-negative 
such that
for every 
.
to the following system:
![\[\frac{\sin^2A+\sin^2B+\sin^2C}{\cos^2A+\cos^2B+\cos^2C} = 2\]](http://latex.artofproblemsolving.com/9/2/a/92a524bbdca92e9dd4091275714bf346bad96cd7.png)
be a parallelogram and points 
be on its exterior. If triangles 
and 
are similar, i.e. 
, prove that triangle 
is similar to these two triangles.
be a triangle and let be a point not lying on any of the three lines 
, 
, or 
. Distinct points 
, 
, and 
lie on lines , 
, and , respectively, such that 
and 
. Show that there exists a point on the circumcircle of 
such that 
is similar to 
.
be the intersection point of medians in the acute-angled triangle 
,
and 
.Prove that is equilateral triangle.
be the point of symmetry of with respect to the midpoint of ,then quadrilateral 
is a parallelogram,which follows that 
,and hence 
are concyclic.Therefore 
,and 
.So 
,then 
is a diameter of the circumcircle of ,and 
.Combining 
,we get that is equilateral,as desired.
and 
,
lies in the same circle. But we also know that 
collinear and 
,
are same, and thus