c#画正弦波

/// <summary>
/// 画正弦曲线
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button2_Click(object sender, EventArgs e)
{
Bitmap bitmap = new Bitmap(pictureBoxFrequencyDomain.Width, pictureBoxFrequencyDomain.Height,   PixelFormat.Format32bppArgb);

Graphics g = Graphics.FromImage(bitmap);
Pen pen = new Pen(Color.Red, 1);
double x1 = 10;
double y1 = 0;
for (double x = 1; x < pictureBoxFrequencyDomain.Width; x++)
{
//SIN最大值为1,而我图上用了100像素,所以有
//100/1=100 故而y要乘100;
// x/180*Math.PI 这个表达式把角度换成弧度值
double y = Math.Sin(x / 180 * Math.PI)*60;

//SIN值一个循环为360度，而我图上用了200像素表示，所以有：
//360/200=1.8 故而x值要除1.8
g.DrawLine(pen, (float)x1, (float)y1 + 60, (float)(x / 1.8) + 10, (float)y + 60);
x1 = x / 1.8 + 10;
y1 = y;
}

pictureBoxFrequencyDomain.Image = bitmap;
}