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Nov 19th, 2017
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  1. r[t_] := {t, t^2, t^3}
  2.  
  3. uT[t_] = Simplify[ r'[t] / Norm[ r'[t] ], t ∈ Reals];
  4. vN[t_] = Simplify[ uT'[t]/ Norm[ uT'[t]], t ∈ Reals];
  5. vB[t_] = Simplify[ Cross[r'[t], r''[t]] / Norm[ Cross[r'[t], r''[t]] ], t ∈ Reals];
  6.  
  7. {uT[t], vN[t], vB[t]} // Column // TraditionalForm
  8.  
  9. Simplify[ Norm /@ {uT[t], vN[t], vB[t]}, t ∈ Reals]
  10.  
  11. {1, 1, 1}
  12.  
  13. Animate[
  14. Show[ ParametricPlot3D[ {r[t]}, {t, -1.3, 1.3}, PlotStyle -> {Blue, Thick}],
  15. Graphics3D[{ {Thick, Darker @ Red, Arrow[{r[s], r[s] + uT[s]}]},
  16. {Thick, Darker @ Green, Arrow[{r[s], r[s] + vB[s]}]},
  17. {Thick, Darker @ Cyan, Arrow[{r[s], r[s] + vN[s]}]}}],
  18. PlotRange -> {{-2, 2}, {-2, 2}, {-2, 2}}, ViewPoint -> {4, 6, 0},
  19. ImageSize -> 600],
  20. {s, -1, 1}]
  21.  
  22. frame[r_] := Function[{t}, Evaluate[FullSimplify[
  23. Append[#, Cross @@ #] &@ Orthogonalize[D[r[t], {t, #}] & /@ {1, 2}, Dot],
  24. Assumptions -> t [Element] Reals]]]
  25.  
  26. frame[{#, #^2, #^3} &][t] // TraditionalForm
  27.  
  28. bigT={1,2t,3t^2}/Sqrt[1+4 t^2+9 t^4]
  29.  
  30. bigT/. t-> 2
  31.  
  32. BigTFunction[x_]:= {1,2x,3x^2}/Sqrt[1+4 x^2+9 x^4]
  33.  
  34. BigTFunction[2]
  35.  
  36. FrenetSerretSystem[{ x1, ..., xn}, t] gives the generalized curvatures
  37. and Frenet-Serret basis for the parametric curve x[t]
  38. i.e.
  39. it returns {{ k1, ..., k(n-1)}, { e1, ..., en}}, where ki are generalized curvatures
  40. and ei are the Frenet-Serret basis vectors.
  41.  
  42. FrenetSerretSystem[ r[t], t] // TraditionalForm
  43.  
  44. r[t_] := {t, t^2, t^3}
  45.  
  46. FrenetSerretSystem[ r[t], t] // Last // Simplify // Column // TraditionalForm
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