http://mathsci.kaist.ac.kr/pow/
Concluding 2012 Spring
Thanks all for participating POW actively. Here’s the list of winners:
- 1st prize: Park, Minjae (박민재) – 2011학번
- 2nd prize: Lee, Myeongjae (이명재) – 2012학번
- 3rd prize: Suh, Gee Won (서기원) – 수리과학과 2009학번
- 4th prize: Cho, Junyoung (조준영) – 2012학번
- 5th prize: Kim, Taeho (김태호) – 수리과학과 2011학번
Solution: 2012-12 Big partial sum
Let A be a finite set of complex numbers. Prove that there exists a subset B of A such thatThe best solution was submitted by Minjae Park (박민재), 2011학번. Congratulations!
∣∣∑z∈Bz∣∣≥1π∑z∈A∣z∣.
Here is Solution of Problem 2012-12.
Two incorrect solutions were submitted (M.J.L., W.S.J.).
Solution: 2012-11 Dividing a circle
Let f be a continuous function from [0,1] such that f([0,1]) is a circle. Prove that there exists two closed intervalsThe best solution was submitted by Myeongjae Lee (이명재), 2012학번. Congratulations!I1,I2⊆[0,1] such thatI1∩I2 has at most one point,f(I1) andf(I2) are semicircles, andf(I1)∪f(I2) is a circle.
Here is his Solution of Problem 2012-11.
Alternative solution was submitted by 박민재(2011학번, +3). Two incorrect solutions were submitted (W.S.J., K.M.P.).
2012-13 functions for an inequality
Determine all nonnegative functions f(x,y) and g(x,y) such that
(∑i=1naibi)2≤(∑i=1nf(ai,bi))(∑i=1ng(ai,bi))≤(∑i=1na2i)(∑i=1nb2i)
for all reals ai , bi and all positive integers n.
2012-12 Big partial sum
Let A be a finite set of complex numbers. Prove that there exists a subset B of A such that
∣∣∑z∈Bz∣∣≥1π∑z∈A∣z∣.
Solution: 2012-10 Platonic solids
Determine all Platonic solids that can be drawn with the property that all of its vertices are rational points.The best solution was submitted by Myeongjae Lee (이명재), 2012학번. Congratulations!
Here is his Solution of Problem 2012-10.
Alternative solutions were submitted by 박민재 (2011학번, +3, Solution), 정우석 (서강대학교 2011학번, +3), 박훈민 (대전과학고 2학년, +2). One incorrect solution was submitted (G.S.).
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