class Trapecios extends Program {
  void run() {
    print  (" area sin(x)= " + new FunSin().area(0.0, PI/2, 100));
    println(" area sin(x)= " + new FunSin().area(0.0, PI/2, 1000));
    print  (" area exp(x)= " + new FunExp().area(0.0, 1.0, 100));
    println(" area exp(x)= " + new FunExp().area(0.0, 1.0, 1000));
    print  (" area x^3= " + new FunXk(3).area(0.0, 1.0, 100));
    println(" area x^3= " + new FunXk(3).area(0.0, 1.0, 1000));
  }
}

class Funcion extends Program {
  double eval(double x) {
    return 0.0;
  }
  double area(double a, double b, int n) {
    double delta= (b-a)/n;
    double sum= (eval(a)+eval(b))/2; // 1/2*(f(a)+f(b))
    double x= a;
    for (int i=1; i<n; i++) {        // + f(a+i*delta), con i=1 ... n-1
      x= x+delta;
      sum= sum+eval(x);
    }
    return delta*sum;
  }
}

class FunSin extends Funcion {
  double eval(double x) {
    return sin(x);
  }
  // area se hereda
}
class FunExp extends Funcion {
  double eval(double x) {
    return exp(x);
  }
  // area se hereda
}
class FunXk extends Funcion {
  int k;
  FunXk(int k) {
    this.k= k;
  }
  double eval(double x) {
    return pow(x, k);
  }
  // area se hereda
}