#define _USE_MATH_DEFINES
#include <math.h>
#include <locale.h>
#include <stdio.h>

double funx(double phi, double r, double m, double h)
{
    return r*(m+1)*(cos(m*phi)-h*cos((m+1)*phi));
}

double funy(double phi, double r, double m, double h)
{
    return r*(m+1)*(sin(m*phi)-h*sin((m+1)*phi));
}

double Length(double Left,double Right,long N,double (*funx)(double, double, double, double), double (*funy)(double, double, double, double))
{
    double dphi,res=0.0,r=M_PI,m=1./3,h=0.15,phi;
    dphi = (Right - Left) / N;
    for (phi = Left; phi <= (Right-dphi); phi+=dphi)
        res += sqrt(pow((funx(phi+dphi,r,m,h)-funx(phi,r,m,h)),2)+pow((funy(phi+dphi,r,m,h)-funy(phi,r,m,h)),2));
    res += sqrt(pow((funx(Right,r,m,h)-funx(phi,r,m,h)),2)+pow((funy(Right,r,m,h)-funy(phi,r,m,h)),2));
    return res;
}

int main()
{
    long n;
    double  L = 0.0, R = 6.0*M_PI;
    double  V, V0=28.74656728; //28.74657809
    setlocale( LC_ALL, "" );
    printf("Число шагов;Относительная ошибка\n");
    for (n = 1; n < 1000; n+=n/50+1) {
        V = Length(L, R, n, funx, funy);
        printf( "%ld;=%.15G\n", n, V-V0);
    }
    return 0;
}