[Class 01] Background 1b f is not updated

[ivanightingale]

f is defined at

LearningToControlClass/class01/background_materials/math_basics.jl

Line 99 in 73b7ad5

f(t) = dot(a, t)

and should be updated for part b). ans2 = a is marked as correct but that's actually the answer to the previous part.

[andrewrosemberg]

Thank you!