double cos(double c){
double x=c;
if(x>PI*2)x-=PI*2;
int N = 2*20;
double mx2 = -x*x;

    int i;
    double part = 1, sum = 1;
    for (i = 2; i < N; i+=2) {
        part *= mx2/((i-1)*i);
        sum += part;
    }
  return sum;
}
//синус,из косинуса
double sin(double x){return cos(((PI/2.0)-x));}