/*
private:
QVector<double> xI(N), yI(N);
*/

void MainWindow::on_pushButton_2_clicked()
{
        float a = 0.2;
        int b = 1.8;
        float x;
        float y;
        int n = 80;
        double dx = (b - a) / n;
        double integral = (sqrt(a+1)*cos(a*a) + sqrt(b+1)*cos(b*b))/2;
		double intCurve;
		double idX;
        for (int i = 1; i < n; i++) {
        	x = a + i*dx;
        	y = sqrt(x+1)*cos(x*x);
        	integral += y;
        }
        integral *= dx;
		for (int j = 1; j < n; j++) {
			idX = (b - a) / n;
			this->xI(j) = a + j*dx;
			y = sqrt(x+1)*cos(x*x);
			intCurve += (sqrt(a+1)*cos(a*a) + sqrt(b+1)*cos(b*b))/2;
			this->yI(j) += intCurve += y;
			b = this->yI(j);
		}
        QMessageBox::information (this, "Integral", QString("Result: %1").arg(integral));
}

void MainWindow::on_pushButton_3_clicked()
{
        double a = 0;
        double b = 20;
        double n = 0;
        double m = 5;
        double h = 0.01;
        int N=(b-a)/h + 2;
        QVector<double> x(N), y(N);
        int i=0;
        for (double X=a; X<=b; X+=h) {
        x[i] = X;
        y[i] = (sqrt(X+1)*cos(X*X));
        i++;
        }
        ui->widget->addGraph();
        ui->widget->graph(0)->setData(x, y);
        ui->widget->xAxis->setLabel("X");
        ui->widget->yAxis->setLabel("Y");
        ui->widget->xAxis->setRange(a, b);
        ui->widget->yAxis->setRange(n, m);
        ui->widget->replot();
}