m/Geometry·Rohan D.·2h agoQuestion Answered2 comments
Is there a proof of Ptolemy without inversion?
Every proof I know of uses inversion or complex numbers. Is there a purely synthetic one?
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m/ProblemOfTheDay·Meera P.·5h agoApproach0 comments
Yesterday’s NT-H: three different ways in
Euclid’s argument is the classic. You can also use , or the pairwise coprime Fermat numbers .
m/ProblemOfTheDay·Nikhil G.·45m agoQuestion0 comments Log in to reveal
Today’s ALG-M: is f(x) = x the only non-zero solution?
Setting gives , so or …
m/Algebra·Kabir S.·7h agoApproach0 comments
A slick proof of AM–GM for three variables
Start from and the inequality drops out.
m/Combinatorics·Zara M.·3h agoQuestionNeeds an answer0 comments
Stars and bars: when do I need the extra constraint trick?
I keep forgetting whether to subtract first or count everything and remove the bad cases. Is there a rule of thumb?
m/Resources·Priya K.·1d agoResource0 comments
Books that actually helped me for INMO
Engel’s Problem-Solving Strategies, Challenge and Thrill of Pre-College Mathematics, and Evan Chen’s EGMO. What would you add?
m/General·Liminal Team·2d agoPinned0 comments
Welcome to the Liminal community
This is where students talk about problems, share approaches and ask questions. Read freely. Log in when you want to post. Please share how you thought, not only what the answer was.
m/General·Liminal Team·3d agoPinned0 comments
How to write a solution others can learn from
Start with what you tried first, even if it failed. Then show the idea that worked, and say why it worked. Keep the final answer for the last line.
These are examples. Log in to read and join the real discussions.Open the forum
Peer circles
Six students, one mentor, a lot of arguing. A circle is where you present your proofs and learn to critique others.
Think out loud, with people who push back.Circles are matched by level and topic after Chapter Zero, so everyone in the room is working at the same edge.
STEP 01Sit Chapter ZeroTwo rounds that show how you think, not what you have memorised.
STEP 02Get placedBeginner or Advanced, based on where your maths is today.
STEP 03Meet your circleWeekly sessions. Present a proof, critique a proof, repeat.
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