study 6-9 枝分かれをつなぐ曲線
https://scrapbox.io/files/682b625e55bf44ae3d2c18ff.png
https://scrapbox.io/files/682b6252ae0cf75404083056.png
https://scrapbox.io/files/682b6256bfb74766e45ee4db.png
https://scrapbox.io/files/682b625a9173ddfda614adff.png
https://scrapbox.io/files/682b6262f85a3039f5a591b4.png
https://scrapbox.io/files/682b62667cae8aa6463affc2.png
https://scrapbox.io/files/682b626b1a11f60f15320084.png
https://scrapbox.io/files/682b626e0ce9748cb0a1fd95.png
https://scrapbox.io/files/682b627219a79226ee633e73.png