Definition of f

f[x_, y_] := (E^Sin)[50 x] + 
          Sin[60 (E^y)] + Sin[70 Sin[x]] + Sin[Sin[80 y]] - 
          Sin[10 (x + y)] +  ((x^2) + (y^2))/4;
f[{x_, y_}] := f[x, y];

Session p. 82

NMinimize[{f[x, y], (x^2) + (y^2) ≤ 1}, {x, y}, 
      Method -> {"DifferentialEvolution", "SearchPoints" -> 
            250}]