MathDB
2023 China TST Problem 6

Source: 2023 China TST Problem 6

March 14, 2023
algebraChina TST

Problem Statement

Prove that: (1) In the complex plane, each line (except for the real axis) that crosses the origin has at most one point z{z}, satisfy 1+z23z64R.\frac {1+z^{23}}{z^{64}}\in\mathbb R. (2) For any non-zero complex number a{a} and any real number θ\theta, the equation 1+z23+az64=01+z^{23}+az^{64}=0 has roots in Sθ={zCRe(zeiθ)zcosπ20}.S_{\theta}=\left\{ z\in\mathbb C\mid\operatorname{Re}(ze^{-i\theta })\geqslant |z|\cos\frac{\pi}{20}\right\}. Proposed by Yijun Yao