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if(ui->Drob->isChecked()==1)    {        double x1,x2,xn,h=0.1,mod;                x1=point.x();                double tochka=x1;                xk[0]=x1;                yk[0]=FF.Parser(str,x1);//                xk[0]=xk[1];//                yk[0]=yk[1];                x2=x1+h;                mod=x2-x1;                while(mod>0.001)                {                                if( FF.Parser(str,x2)<FF.Parser(str,x1))                                {                                    h=(-1)*h/2;                                }                        x1=x2;                        x2=x2+h;                        mod=fabs(x2-x1);                }                double tmpx1=x2;                h=0.1;                x1=point.x();                x2=x1+h;                mod=x2-x1;                while(mod>0.001)                {                                if( FF.Parser(str,x2)>FF.Parser(str,x1))                                {                                    h=(-1)*h/2;                                }                        x1=x2;                        x2=x2+h;                        mod=fabs(x2-x1);                }                double tmpx2=x2;                if(fabs(tmpx2-tochka)>fabs(tmpx1-tochka))                    xk[1]=tmpx1;                else                    xk[1]=tmpx2;                yk[1]=FF.Parser(str, xk[1]);//                Вывод результата                rez.setNum(xk[1]);                rez.remove(6,rez.length()-6);                ui->rezult->setText(rez);                Curve2->setData(xk, yk, 2);                Curve2->setVisible(true);                CurveToch->setData(xk, yk, 2);                CurveToch->setVisible(true);                ui->graf->replot();