WPF canvas plot sin and cos function

//xaml
<Window x:Class="WpfApp11.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp11"
        mc:Ignorable="d"
        Title="Simple Line Chart" Height="450" Width="800">
    <Grid Margin="0"
          x:Name="chartGrid" 
          ClipToBounds="True"
          Background="Transparent"
          SizeChanged="Grid_SizeChanged">
        <Border HorizontalAlignment="Center"
                    VerticalAlignment="Center"
                    BorderBrush="Gray"
                    BorderThickness="1"
                    Background="White"
                    Margin="0">
            <Canvas Margin="0"
                    x:Name="chartCanvas"
                    ClipToBounds="True"
                    Background="Transparent">
                
            </Canvas>
        </Border>
                    
    </Grid>
</Window>


//cs
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp11
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private double xmin = 0;
        private double xmax = 6.5;
        private double ymin = -1.1;
        private double ymax = 1.1;
        private Polyline pl;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void AddChart()
        {
            pl=new Polyline();
            pl.Stroke=Brushes.Black;
            for (int i = 0; i<70; i++)
            {
                double x = i/5.0;
                double y = Math.Sin(x);
                pl.Points.Add(NormalizePoint(new Point(x, y)));
            }

            chartCanvas.Children.Add(pl);   

            //Draw cosine curve
            pl=new Polyline();
            pl.Stroke=Brushes.Black;
            pl.StrokeDashArray=new DoubleCollection(new double[] { 4, 3 });

            for(int i=0;i<70;i++)
            {
                double x = i/5.0;
                double y = Math.Cos(x);
                pl.Points.Add(NormalizePoint(new Point(x, y)));
            }
            chartCanvas.Children.Add(pl);
        }

        private Point NormalizePoint(Point pt)
        {
            Point result=new Point();
            result.X=(pt.X-xmin)*chartCanvas.Width/(xmax-xmin);
            result.Y=chartCanvas.Height-(pt.Y-ymin)*chartCanvas.Height/(ymax-ymin);
            return result;
        }

        private void Grid_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            chartCanvas.Width=chartGrid.ActualWidth;
            chartCanvas.Height=chartGrid.ActualHeight;
            chartCanvas.Children.Clear();
            AddChart();
        }
    }
}