Show that for any triangle T and any Jordan curve C in the Euclidean plane, there exists a triangle inscribed in C which is similar to T.

The best solution was submitted by 강한필 (전산학부 2016학번, +4). Congratulations!

Here is his solution of problem 2021-02.

Other solutions was submitted by 하석민 (수리과학과 2017학번, +3), 박은아 (수리과학과 2015학번, +2).

Prove that for any given positive integer \( n \), there exists a sequence of the following operations that transforms \( n \) to a single-digit number (in decimal representation).

1) multiply a given positive integer by any positive integer.

2) remove all zeros in the decimal representation of a given positive integer.

The best solution was submitted by 강한필 (전산학부 2016학번, +4). Congratulations!

Here is his solution of problem 2021-01.

Other solutions was submitted by 김기수 (수리과학과 2018학번), 박은아 (수리과학과 2015학번, +3), 전해구 (기계공학과 졸업생).

Compute \[ \lim_{n\to \infty} \cos^{2016} (\pi\sqrt{n^2+4n+9}).\]

The best solution was submitted by Kang, Hanpil (강한필), 2016학번. Congratulations!

Here is his solution of problem 2016-8.

Alternative solutions were submitted by 국윤범 (수리과학과 2015학번, +3), 이준호 (2016학번, +3), 장기정 (수리과학과 2014학번, +3), 유찬진 (수리과학과 2015학번, +3), 배형진 (마포고등학교 2학년, +3), 박기연 (2016학번, +3), 유현우 (한양대학교 화학공학과 2013학번, +3), 윤준기 (전기및전자공학부 2014학번, +3), 김재현 (2016학번, +3), 이예찬 (오송고등학교 교사, +3), 최백규 (2016학번, +3), 장창환 (기계공학과 2015학번, +3), 한대진 (인천예일중학교 교사, +3), 박은구 (연세대 수학과 대학원생, +3), 김태균 (2016학번, +3), 박정우 (한국과학영재학교 2016학번, +3), 이원웅 (건국대 수학과 2014학번, +3), 이상민 (수리과학과 2014학번, +3).