[83] 加法定理無し、半角の公式と倍角の公式の図形的証明 プトレマイオス 数学史

Contents: Thanks for watching. This video is all about half-angle and double-angle formulas form the perspective of geometrical explanation and mathematical history. Claudius Ptolemaeus largely contributed to making the table of trigonometrical function, astronomy, and geometry in a quite practical way even about 2000 years ago. Furthermore, he had a massive influence until Medieval Europe. 動画の内容：半角の公式と倍角の公式の図形的理解です。人によっては現代的には証明というほど大それたものではないかも知れませんが、加法定理の源泉になるものですし数学史的にも非常に意味のある図形的解釈であります。プトレマイオスが三角表を作り天文学や測量に大きな経験をした有難いものです。 -------------------------------------------------------------------------------- 主に数学に関することを動画にしています。みんなで面白いことをあーだこーだ言えたらいいなと。 動画に関するアドバイス（声量・ライト・ペン・板書など）や動画にしてほしいことなど何でも受け付けております。むしろください。 連絡等はこちらに→maths.toshi@gmail.com Thanks a ton for visiting here and reading this. Please subscribe this channel and give this video a like if you like it. I usually make videos about mathematics, but any kinds of topics which I find interesting and attractive. All I want to do is just discuss and talk about them, and communicate with people who are into maths, after all. I am afraid to say that I basically speak in Japanese in my videos; however, I am going to try and write things down in the way everyone can comprehend what they are, not without mathematics literacy at least :-). I would appreciate if you gave me any kind of advice ranging from the topics you would like me to bring about to the volume, my handwriting, and the lighting in my videos. Please do not hesitate to leave any comments for this channel growth, and help me to enrich this channel.