#include
#include
double g,m,c,a0,l,pi=3.14;
#define MAXN 10
void rzut(double t,double y[],double f[])
{
f[0]=y[1];
f[1]=-g/l*sin(y[0]);
}
void vrk4( double x0, double y0[], double h, int n, void (*fun)(double, double*, double*), double y1[] );


void main()
{double t,v,dt,tk;
g=9.81;m=2.;c=.003;a0=pi/18.;l=2.;
double y[2],y1[2];


printf("podaj dt i tk\n");
scanf("%lf%lf",&dt,&tk);
//wp
t=.0;
y[0]=a0;
y[1]=.0;
//całkujemy
while(t<=tk)
{
vrk4(t,y,dt,2,rzut,y1);
t=t+dt;
printf("t=%lf v=%lf\n",t,y1[1]);
y[0]=y1[0];
y[1]=y1[1];

}
}



void vrk4( double x0, double y0[], double h, int n, void (*fun)(double, double*, double*), double y1[] )
{
int i;
double k1[MAXN], k2[MAXN], k3[MAXN], k4[MAXN];
double ytmp[MAXN];

fun( x0, y0, k1);
for ( i=0; i {
k1[i] *= h;
ytmp[i] = y0[i] + k1[i]/2.0;
}

fun( x0+h/2.0, ytmp, k2);
for ( i=0; i {
k2[i] *= h;
ytmp[i] = y0[i] + k2[i]/2.0;
}

fun( x0+h/2.0, ytmp, k3);
for ( i=0; i {
k3[i] *= h;
ytmp[i] = y0[i] + k3[i];
}

fun( x0+h, ytmp, k4);
for ( i=0; i k4[i] *= h;

for ( i=0; i y1[i] = y0[i] + (k1[i] + 2.*k2[i] + 2.*k3[i] + k4[i])/6.;

}