ООП 3

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            double x = Convert.ToDouble(textBox1.Text),
            y = Convert.ToDouble(textBox2.Text),
            r = Convert.ToDouble(textBox3.Text),
            a = Convert.ToDouble(textBox5.Text),
            b = Convert.ToDouble(textBox6.Text);

            if (((x >= -r) && (x <= 0) && (y <= 0) && (y >= -b) && (Math.Sqrt(Math.Pow(x, 2) + Math.Pow(y, 2)) <= r)) | ((x <= a) && (x >= r) && (y >= 0) && (y <= -b) && (Math.Sqrt(Math.Pow(x, 2) + Math.Pow(y, 2)) <= r)))
            {
                textBox4.Text = "Точка (" + x.ToString() + ", " + y.ToString() + ") входит в область";
            } else {
                textBox4.Text = "Точка (" + x.ToString() + ", " + y.ToString() + ") не входит в область";
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            textBox1.Text = "";
            textBox2.Text = "";
            textBox3.Text = "";
            textBox4.Text = "";
        }

        private void button3_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}