複素数 円 - SERP Analysis

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https://www.chart.co.jp/subject/sugaku/suken_tsushin/35/35-1.pdf

https://math.nakaken88.com/textbook/basic-complex-plane-and-circle/

https://manabitimes.jp/math/1561

https://hiraocafe.com/note/complex-shapes.html

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https://www.mathsoc.jp/outreach/2019aki/nakanishi20190916.pdf