C, Julia, Python, Maxima, Mathematica, ChatGPT and Numerical Errors

Not sure what the poster is getting at. It seems to be 'normal' case of precision with floating point. In Julia for example, you can define u to be BigFloat (defaulting to 32 bytes for me below). It gets you the correct answer. The python and other default versions of other software are definitely not the "right" answer.

  julia> u::BigFloat = 5.0;
  julia> for i=0:72
           u = 6.0*cos(u)
       end
  julia> print(u)
 
 2.77675840848277346491725024972478163010030433082748210024033940771878181653911