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.
, where 
and 
are positive integers satisfying:
such that 
, 
, and 
are pairwise tangent to each other. Find the radius of the circle that is externally tangent to all three of these circles.
, 
, or 
, such that no two consecutive stars have the same letter.
be positive real numbers such that 
. Prove that:
. All of the nine digits are different. Determine which digit does not appear on the board.
problems in a meeting. For each 
, each leader will talk about the 
-th problem for -th minutes. The chair can assign one leader to talk about a problem of his choice, but he would have to wait for the leader to complete the entire talk of that problem before assigning the next leader and problem. The next leader can be the same leader. The next problem can be a different problem. Each leader’s longest idle time is the longest consecutive time that he is not talking.
so that the chair can ensure that the longest idle time for any leader does not exceed .
be the final value obtained after repeatedly summing the digits of until a single-digit number is reached. (For example: 
, because the digit sum of 
is 
and the digit sum of is 
). Evaluate the sum:
be the set of non-negative integer powers of and 
, 
. For every 
and 
in satisfying 
Find the minimum value of 
.
be a circle on the plane. Let 
and 
be circles which are internally tangent to at points 
and 
respectively. Let the centers of and be 
and 
respectively and let the intersection points of and be 
and 
. Assume that lies on the line 
. Let the common external tangent of and that is closer to point be tangent to the circles and at 
and 
respectively. Let the second intersection point of the line 
and be 
and let the second intersection point of the circumcircle of 
and be . Let the circumcenter of 
be 
and let the intersection points of 
and 
be 
. Prove that
on a plane, such that the angle between the two consecutive rays is 
. A point 
is located on the first ray. The projection of onto the second ray is denoted as 
. Similarly, the projection of onto the third ray is 
, and this process continues until the projection of 
onto the seventh ray is 
. Find the ratio 
. on a circle and points 
and 
on segment , such that 
Find the ratio 
, where 
is a point on arc , such that 
is maximized.
