Parmalat

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CCBLC

Pot cu echeru'. Ma duc sa caut un compas.

gabyteodor

Pas 1. Pornim cu latura AB.
Se gaseste mijlocul laturii AB si se construieste cercul cu centrul in acest punct si raza egala cu AB/2 in exteriorul patrulaterului.
Conform unei teoreme orice punct de pe acest semicerc face cu AB un triunghi dreptunghic.

Se procedeaza la fel pentru restul laturilor.
Mai departe astept sugestii :D

gabyteodor

Singura chestie care am gasit-o pana acum este ca daca ducem diagonalele si aflam mijloacele lor, acestea vor fi mereu pe o dreapta care trece prin mijlocul patratului: una pe verticala cealalata pe orizontala

catanedelcu

A personal story of Tanya Khovanova

In the summer of 1975, while I was in a Soviet math camp preparing to compete
in the International Math Olympiad on behalf of the Soviet Union, my fellow
team members and I were approached for help by Valera Senderov, a math
teacher in one of Moscow's best special math schools.
The Mathematics Department of Moscow State University, the most pres-
tigious mathematics school in Russia, was at that time actively trying to keep
Jewish students (and other \undesirables") from enrolling in the department.
One of the methods they used for doing this was to give the unwanted students a
diferent set of problems on their oral exam. I was told that these problems were
carefully designed to have elementary solutions (so that the Department could
avoid scandals) that were nearly impossible to find. Any student who failed
to answer could easily be rejected, so this system was an effective method of
controlling admissions. These kinds of math problems were informally referred
to as “Jewish" problems or “coffins" is the literal translation from
Russian; they have also been called “killer" problems in English.

catanedelcu

These problems and their solutions were, of course, kept secret, but Valera
Senderov and his friends had managed to collect a list. In 1975, they approached
us to solve these problems, so that they could train the Jewish and other students
in these mathematical ideas. Our team of the best eight Soviet students, during
the month we had the problems, solved only half of them. True, that we had
other priorities, but this fact speaks to the diffculty of these problems.
Being young and impressionable, I was shaken by this whole situation. I had
had no idea that such blatant discrimination had been going on. In addition
to trying to solve them at the time, I kept these problems as my most valuable
possession|I still have that teal notebook.
Later, I emigrated to the United States. When I started my own web page,
one of the first things I did was to post some of the problems. People sent me
more problems, and solutions to the ones I had. It turned out that not all of
the coffins even had elementary solutions: some were intentionally ambiguous
questions, some were just plain hard, some had impossible premises. This article
is a selection from my collection; we picked out some choice problems that do
contain interesting tricks or ideas.
Tanya Khovanova

Maseru

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ile

Imagine ataşată
eu am luat-o de la coada la cap...latura BC am fixat-o la un colt de foaie,am incadrat figura in patrat si dupaia am verificat patratul in cerc

ile

@latura CD

disdediseara

Nu faceti asta acasa:
Am luat patru sticle de bere pe care le-am numit A,B,C si D.Continutul sticlelor l-am folosit in scop didactic,ca sursa de inspiratie si curaj.Sticlele A,B si C am reusit sa le potrivesc pe planul drept si patrat al mesei.Cu D-ul a fost mai greu.S-a deplasat in jos spre planul covorului intr-o fuga pe care eu o consider cel putin rusinoasa.Noroc ca mai aveam inca vreo doua D-uri de bere si patru H-uri de vin in frigider.E-uri nu tin ca nu-s bune nici in alimente.Deci,am luat D-ul din frigider si l-am convins sa ramana pe masa.Apoi am incercat sa desenez un patrat.Nu mi-a iesit deloc.Cred ca problema survenea de la faptul ca eu nu ma mai puteam deplasa decat in cercuri.O alta problema,nu aveam rigla.Noroc cu nevasta-mea ca veni cu ea in mana fluturand-o amenintator.Intre noi fie vorba,semana mai mult a facalet.M-am retras in dormitor cu niste compasi suficienti de mari, reusind sa inchid usa pe dinauntru.
 Acum stau sa ma gandesc,nu era mai bine sa fi incercat de la inceput cu H-urile.

Maruii

Desenam un sistem cartezian xoy.
Pe axa ox se afla punctul B.
Pe axa oy se afla punctul C.
Proiectia punctului D pe OY = D' si D" pe OX.
Proiectia punctului C pe OY =C' si C" pe OX.
Verificam care din dreptele obtinute pe axa ox sunt egale ca lungime pe axa oy cu ajutorul compasului sau masuram cu rigla.
Observam ca OD'= OC".
Trasam perpendiculare pe sistemul cartezian XOY din punctele D' si C" iar intersectia lor (I) va forma al 4 punct al patratului  D'OCI.

Maruii

D'OC"I