$\it\scalebox{2}{%n}$

$\it\scalebox{2}{%n}$

$\it\scalebox{2}{%n}$

$\huge{%n}$

$\it\scalebox{2}{%n}$

$\it\scalebox{2}{%n}$

$\Large{%n}$

r = 1 (slider from 0 to 3)
A: (0, 0)
B: A + (((2 * π) * r), 0)
C = Point(Segment[A, B])
f = Segment(A, C)
O: C + (0, r)
C' = Rotate(C, ((-f)) / r, O)
c = CircleArc(O, C, C')
fontsize_1 = 2 (slider from 2 to 7, step 0.1)
d = If(C ≟ A, Circle[O, r])

Tool: 简易坐标系
请选择原点，分别输入：x最小、最大值，y最小、最大值
Input: A, a, b, c, d
Output: B, C, O, u, v

$\huge\textcolor{}{x}$

$\huge\textcolor{}{y}$

$\Large\textcolor{}{O}$

A: (0, 0)
u = Vector(A + (a - 1, 0), A + (b + 1, 0))
v = Vector(A + (0, c - 1), A + (0, d + 1))
B: A + (b + 1, 0)
C: A + (0, d + 1)
O: A