What to do if the program gives an error when entering the double function?

Question

C++ / C#

#include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;
//Функция для полинома:
double F(double x) {
  return 5 * tan(x) - (10 / (x) ^ 2) - 3;
}
//Функция поиска корня:
double FindRoot(double (*f)(double), double a, double b, double eps) {
  double c;
  while ((b - a) / 2 > eps) {
    c = (a + b) / 2;
    if ((f(a) * f(c)) > 0) a = c;
    else b = c;
  }
  return c;
}
int main() {
  //Интервал, погрешность и корень:
  double a, b, eps, x;
  cout << "interval: ";
  cin >> a;
  cin >> b;
  //Проверка корректности интервала:
  if (F(a) * F(b) > 0) {
    cout << "Wrong interval!\n";
    return 0;
  }
  cout << "error: ";
  cin >> eps;
  //Поиск решения:
  x = FindRoot(F, a, b, eps);
  cout << "x = " << x << endl;
  return 0;
}

when you enter this program, you get error E2140 "expression must be an integer or enumeration type with no scope"

Answer 1

It would be nice to write in which line the error is (and for starters, format the code normally - there is a button in the editor).
Apparently, the problem here return 5 * tan(x) - (10 / (x) ^ 2) - 3;
(x) ^ 2is not exponentiation, but XOR (exclusive OR). Squaring like this: x*xfor example