The plots in this Demonstration show precision error. The formula arctan(x)+arctan(1/x)=π/2 is true for all real x≠0. To plot arctan(kx)+arctan(1/(kx))-π/2 for various k, Mathematica correctly finds numerical values very close to 0. In the plot, these infinitesimal deviations are magnified a quadrillion-foldComponente Curricular::Educação Superior::Ciências Exatas e da Terra::Matemática