r = 2 (slider from 0 to 5, step 0.1)
c: x^(2) + y^(2) = r^(2)
s = 1.5 (slider from 0 to r * 2 * π, step 0.1)
f(x) = r * cos(x / r)
g(x) = r * sin(x / r)
P: (f(s), g(s))
g_x = Derivative(g, x)
f_x = Derivative(f, x)
e_1 = Vector(P, P + (f_x(s), g_x(s)))
J: {{0, -1}, {1, 0}}
e_2 = Vector(P, P + J * e_1)
f_{xx} = Derivative(f_x, x)
g_{xx} = Derivative(g_x, x)
e'_1 = Vector(P, P + (f_{xx}(s), g_{xx}(s)))
κ: Length[e'_1] / Length[e_2]
text1: "曲率 κ=" + κ + ""