Question

I want to calculate trigonometric ratio in c using series

 sinx = x - x3/3! + x5/5! - x7/7! + a 

and want to compare my result with standard math lib function.
where a = constant

Any help would be appreciated!!

Answer 1

If the question is how to sum up the series, you could just update the term one by one:

double sum_the_series(double x, size_t number_of_terms)
{
  const double x2 = x * x;

  double term = x;
  double result = term;

  for (size_t i = 1; i < number_of_terms; ++i)
  {
    term = term * x2 / (double(2*i) * double(2*i+1));
    if (i % 2 == 0) result += t;
    else            result -= t;
  }

  return result;
}