v(x) = 10.0 * exp(-(0.00866) * x)
A = (-80, 0)
a = OrthogonalLine(A, xAxis)
B = Intersect(v, a, (-80.0, 19.993057594005027))
C = Intersect(v, yAxis, (0.0, 10.0))
v'(x) = -v(x)
vinst'(x) = 4.0 * exp(-(0.00866) * x) * cos(0.7854 * 3.0 - 0.7854 * x)
vinst''(x) = 4.0 * exp(-(0.00866) * x) * cos(0.7854 * 4.5 - 0.7854 * x)
t = -60.6 (slider from -80 to 0, step 0.1)
D: (t, 18.34)
b = OrthogonalLine(C, xAxis)
vinst(x) = 10.0 * exp(-(0.00866) * x) * cos(0.7854 * t - 0.7854 * x)