求大神啊C#出现了targetInvocationException的有关问题

求大神啊！！！C#出现了targetInvocationException的问题
他说我出现了那个问题，发现错在那个输入赋值的地方，也就是timer控件里面的东西，怎么样才能解决？有些代码我删除了，因为太多放不下。

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        const double pi = 3.141592654;
        double δ0, δ1, δ2, δ3;
        double r0, r1, w, h, e0;
        double[] sva = new double[3];
        int i, angle;
        int x1, y1;

       
//初始值
        private void button2_Click(object sender, EventArgs e)
        {
            comboBox1.Text = "(1)偏置(或对心)尖顶推杆盘形凸轮";
            comboBox2.Text = "(2)二次多项式";
            comboBox3.Text = "(3)五次多项式";
            textBox1.Text = "30";
            textBox2.Text = "0";
            textBox3.Text = "0.5";
            textBox4.Text = "10";
            textBox5.Text = "90";
            textBox6.Text = "90";
            textBox7.Text = "90";
            textBox8.Text = "90";
            textBox13.Text = "7";
        }
//start
        private void button3_Click(object sender, EventArgs e)
        {
            timer1.Interval = 500;
            timer1.Enabled = true;
        }
//pause
        private void button4_Click(object sender, EventArgs e)
        {
            timer1.Enabled = false;
        }
//改用数据前请先清零
        private void button5_Click(object sender, EventArgs e)
        {
            Graphics g1 = this.pictureBox1.CreateGraphics();
            Graphics g2 = this.pictureBox2.CreateGraphics();
            Graphics g3 = this.pictureBox3.CreateGraphics();
            Graphics g4 = this.pictureBox4.CreateGraphics();
            Graphics g5 = this.pictureBox5.CreateGraphics();
            g1.Clear(this.BackColor);
            g2.Clear(this.BackColor);
            g3.Clear(this.BackColor);
            g4.Clear(this.BackColor);
            g5.Clear(this.BackColor);
            timer1.Enabled = false;
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
            textBox4.Text = "";
            textBox5.Text = "";
            textBox6.Text = "";
            textBox7.Text = "";
            textBox8.Text = "";
            textBox9.Text = "";