心線相依 The Extensions of Euler Line
此題出處為 Crux Mathematicorum, Vol. 44(4), Apr 2018[1]。已知H為△ABC 的垂心,自A、B與C往對邊̅BC、̅CA與̅AB 作三高,得三垂足為 D、E 與F,從△ABC的三邊往外作矩形,使其寬與三邊上的高成比例,再將這三個矩形相臨的頂點連起來,形成三組三角形。證明這三個三角形的中線會三線共點。事實上這點就是外心。 我將原題延伸為四種建構方法,從△ABC 的三邊往外作平行四邊形,分別連三個外接三角形,考慮其中線、角平分線、中垂線與高,以及三角形的五心。分析三線共點的情形。 本研究最特別之處是在四種建構96種情形中,共有69種共點。其中有7 種情形,當任意點J 配上三中線共點於P時,此時J、重心G與P點三點共線,且̅JG :̅GP=2 :1。當任意點J與垂心重合時,三中線共點於外心,此時這條直線即歐拉線。另外有 11 種情形,當任意點J配上三中線共點於P時,此J、重心G與P點三點共線,且̅JG :̅GP=1: 2。當任意點J與外心重合時,三中線共點於垂心,此時這條直線即歐拉線。且當f1(J,m)=P1,f2 (J , m)=P2,此時P2、P1、重心G與J共線。最特別的是當J與外心重合時, P1 是九點圓的圓心。
The Maximum Area of N-gons within the Intersection Region of Two Congruent Circles
At the 61st National High School Science Fair of Taiwan, the first-rank paper "The Study of the Largest Area of Inscribed Triangle within the Intersection of two circles" was presented. The authors discussed several properties of maximum area of inscribed triangles within intersection regions of two congruent circles. They only claim their results but without providing a rigorous proof. However, we give a proof by showing the convergence of the iteration of finding the largest height. Subsequently, we offer new methods to approach the problems such as the trigonometric identities, Jensen's Inequality to prove the maximum area of triangles and quadrangles within the intersection region of two congruent circles. Finally, we determined the maximum area for the case of n-gons. We conducted further research and discussion on this issue. In the future, we hope to prove why the maximum area of n-gons within the intersection region of two congruent circles occurs when there are two points on the intersection points of the two circles. We aim similar problems in the three-dimensional space, namely the maximum volume of tetrahedron within the intersection of two unit spheres.
Strict Inequalities for the n-crossing Inequality
In2013,Adamsintroducedthen-crossingnumberofaknotK,denoted by cn(K).Inequalities between the 2-, 3-, 4-, and 5-crossing numbers have been previously established.We prove c9(K)≤c3(K)−2 for all knots Kthat are not the trivial, trefoil, or figure-eightknot.Weshowthisinequalityisoptimalandobtainpreviouslyunknownvalues for c9(K).
任意進位制下計數問題的公式解
對於任意正整數m和大於1的正整數p,將集合{m,m+1,...,pm-1}中的每一個元素用p進位制表示。令h為介在1到p-1的正整數,將上述集合在p進位制下有i個h的元素個數記為fh,i(m,p)。本文引進一個創新的想法,讓函數 fh,i(m,p)公式解的推導變得可行且簡單。 再者,當 p=2 時,令 fi(m)= f1,i(m,2),由公式解可以推得對怎樣的正整數n,原像集合the preimage fi-1({n})之元素個數為1。