tmp2

using System;

namespace лаба1
{
    class Program
    {
        const double EPS = 1e-7;
        static void Main(string[] args)
        {
            double x, a, c, y;
            Console.Write("Enter x = ");
            x = Convert.ToDouble(Console.ReadLine());

            Console.Write("Enter a = ");
            a = Convert.ToDouble(Console.ReadLine());

            Console.Write("Enter c = ");
            c = Convert.ToDouble(Console.ReadLine());

            if (check(x, a, c))
            {
                y = f(x, a, c);
                Console.WriteLine($"Result = {y}");
            }
            else
            {
                Console.WriteLine(" it is can not be calculated");
            }
        }
        public static double f(double x, double a, double c) =>

             sqrt_3(c * x - a) + (Math.Log(x, Math.E)) / (2 * Math.Sin(Math.PI / 3 + x));

        public static double sqrt_3(double x)
        {
            if (x < 0) { return -1 * Math.Pow(Math.Abs(x), 1.0 / 3); }
            else { return Math.Pow(x, 1.0 / 3); }
        }

        static bool check(double x, double a, double c)
        {
            return (x > EPS && Math.Abs(2 * Math.Sin(Math.PI / 3 + x)) > EPS);
        }
    }
}