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1955年12月號問题本期問題的解答請讀者在1956年1月20日以前寄至北京德勝門外北京師範大学數学采轉“數学通報數学問題及解答欄工作組”收。所作解答,务請一題一紙,並一一註明姓名。問題的答案及正確解答者的姓名將在本刊1956年3月号的本欄內公佈。本欄欢迎讀者提出適合大家解答德問題,如已有解法,並希把題解作好一併寄來。本欄稿件,概不退还,請勿附邮票。 210.設兩平行綫l与l′交△ABC的BC、CA、AB边(或延长綫)於X、Y、Z与X′、Y′、Z′,自这些交點各作所在边的垂綫,前三垂綫構成△αβγ,後三垂綫構成△α′β′γ′,求証这兩个三角形的外接圆相切。
The December 1955 issue of the issue of this issue was sent to the readers of the Mathematical and Mathematical Questions and Answers Working Group of the Mathematics Bulletin, Beijing Normal University, Beijing Deshengmen, before January 20, 1956. Answer the questions, ask for a piece of paper, and specify the names. The answer to the question and the name of the correct answerer will be published in this column of the March 1956 issue of the journal. This column welcomes readers to put forward suitable questions for everyone to answer the German question. If there is already a solution, then we hope to send it together. Nothing in this column will be returned. Please do not attach stamps. 210. Let two parallel lines l and l′ intersect BC, CA, and AB sides (or extension lines) of △ABC in X, Y, Z and X′, Y′, and Z′. The line, the first three vertical lines constitute Δαβγ, and the last three vertical lines constitute Δα′β′γ′, verifying that the circumcircle of these two triangles is tangent.