国立アメリカ歴史博物館のインスタグラム(amhistorymuseum) - 7月22日 22時30分

Happy Pi Approximation Day! This is observed on July 22 (22/7 in the day/month format) because 22/7 is a common approximation of π. Did you make spiral drawings (like this one) with a Spirograph as a kid? As it turns out, this toy demonstrates some important mathematical concepts. Kinematic models (devices that move) were used to demonstrate straight line motion and curves known as trochoids in engineering and machine design before the digital age. #PiApproximationDay #spirograph #mathematicalmodeling #kinematic #prettymath

[BIHAKUEN]UVシールド(UVShield)

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