double bisekcja(double xp, double xk, double dokl)
{
	if(f(xp)==0.0)return xp;
	if(f(xk)==0.0)return xk;

	double srodek;

	while(xk-xp > dokl)
	{
		srodek = (xp+xk)/2;

		if(f(srodek) == 0.0) return srodek;


		if(f(xp)*f(srodek)<0) xk = srodek;

		else xp = srodek;

	}
	return (xp+xk)/2;
}