개론

https://drive.google.com/uc?id=1-LJnFk98IlprJgvGIfQaTMb7PNRlNyR6

https://drive.google.com/uc?id=1-b9-aSLvIZ0Z1i5KDjqMabl9UZLnETBI

$x = u + tw = u + t(v-u)$