using math.h

I am trying to use asinh from the math.h function. I have included the header file in my project, however it cant find a delcaration of asinh. my function is

void function(double *p, double *x, int m, int n, void *adata)
{
    double *Actual_Output = (double *)adata;
    double Fitted_Curve[5] = {0};
   // double Error_Vector[5] = {0};
    int i;
    double a, b, c;

a = p[0];//parameters
b=p[1];
c=p[2];

  for (i = 0; i <n; i++)
  {

    Fitted_Curve[i] = (1/(a*b))*(c-asinh(sinh(c)*exp(a*(i+1)*2*pi)));
    x[i] = Actual_Output[i]-Fitted_Curve[i];
    //printf("a(x[0]) = %f, b(x[1]) = %f, c(x[2]) = %f\n",p[0], p[1], p[2]);
    //printf("Fitted_Curve= %f\n", Fitted_Curve[i]);
    //printf("Error_Vector= %f\n", x[i]);
    }
}
[code]
Anyone else come across this?

That’s some pretty heavy floating point math for a small memory, 8 bit micro!