b = 0.7 (slider from -1 to 2, step 0.1)
a = 2.35 (slider from 0 to 3.141592653589793, step 0.05)
f(x) = sin(x)
A = Intersect(f, c, (0, 0))
B = Intersect(f, c, (3.141592653487277, 1.0251634020172748E-10))
C: (a, -1)
D: (a, b)
u = Vector(C, D)