Was Bart noch so alles weiß...

a = -8 (slider from -8 to 20, step 0.01)
f(x) = sin(x)
A: (a, f(a))
t = Tangent(A, f)
v = UnitVector(t)
b = 1.4
C: A - b * v
B: A + b * v
d = Segment(B, C)
g(x) = cos(x)
P: (a, g(a))
m = Slope(t)
c = false