OOP LV6 - Zadatak1

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 LV6
{
    public partial class form_trokut : Form
    {
        double a, b, c;
        public form_trokut()
        {
            InitializeComponent();
        }

        double povrsina() {
            double s = (a + b + c) / 2;
            return System.Math.Round(System.Math.Sqrt(s*(s - a)*(s - b)*(s - c)), 2);
        }

        double opseg() {
            return System.Math.Round((a + b + c), 2);
        }

        bool pravokutan()
        {
            if (c == System.Math.Sqrt(a * a + b * b))
            {
                return true;
            }
            return false;
        }

        private void button_izracunaj_Click(object sender, EventArgs e)
        {
            if (!double.TryParse(textBox_a.Text, out a)) {
                MessageBox.Show("Pogrešan unos stranice a!", "Pogreška!");
            }
            else if(!double.TryParse(textBox_b.Text, out b)) {
                MessageBox.Show("Pogrešan unos stranice b!", "Pogreška!");
            }
            else if(!double.TryParse(textBox_c.Text, out c)) {
                MessageBox.Show("Pogrešan unos stranice c!", "Pogreška!");
            }
            else if (c >= a + b || b >= a + c || a >= b + c) {
                MessageBox.Show("Trokut nije moguć!", "Pogreška!");
            }
            else
            {
                label_povrsina.Text = ("Površina: " + povrsina()).ToString();
                label_opseg.Text = ("Opseg: " + opseg()).ToString();
            }
        }

        private void button_pravokutan_Click(object sender, EventArgs e)
        {
            if (!double.TryParse(textBox_a.Text, out a))
            {
                MessageBox.Show("Pogrešan unos stranice a!", "Pogreška!");
            }
            else if (!double.TryParse(textBox_b.Text, out b))
            {
                MessageBox.Show("Pogrešan unos stranice b!", "Pogreška!");
            }
            else if (!double.TryParse(textBox_c.Text, out c))
            {
                MessageBox.Show("Pogrešan unos stranice c!", "Pogreška!");
            }
            else if (c >= a + b || b >= a + c || a >= b + c)
            {
                MessageBox.Show("Trokut nije moguć!", "Pogreška!");
            }
            else
            {
                if (pravokutan())
                {
                    label_pravokutan.ForeColor = System.Drawing.Color.Green;
                    label_pravokutan.Text = "Pravokutan: DA";
                }
                else
                {
                    label_pravokutan.ForeColor = System.Drawing.Color.Red;
                    label_pravokutan.Text = "Pravokutan: NE";
                }
            }
        }

        private void button_izlaz_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }
    }
}