數學資料庫 academic seminar

日期：2011 年 3 月 13 日（星期日）
時間：下午 5 時至 6 時半
地點：香港理工大學 (Rm : BC203)
講者：黃靜小姐（香港中文大學數學系）

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Any other special angles? Algebra knows.

Since we were in junior secondary school, we have already learnt about the trigonometric functions sin, cos and tan, and their values at the special angles 30°, 45° and 60°, for example, cos60°=1/2.

In this seminar, we investigate the possibility for a trigonometric ratio cos(360°/p) to be expressed in terms of distinct radicals and rational numbers, where p is a prime. It turns out that the only two possibilities are p=3 and p=5.

We will use the Galois Theory in abstract algebra to prove this result.