F=2
f0(x,y0,y1,y2,y3)=y2*Cos(y3)
f1(x,y0,y1,y2,y3)=y2*Sin(y3)
f2(x,y0,y1,y2,y3)=F-y2-Sin(y3)-y2
f3(x,y0,y1,y2,y3)=-Cos(y3)/y2
m=MFehlberg([f0(x,y0,y1,y2,y3);f1(x,y0,y1,y2,y3);f2(x,y0,y1,y2,y3);f3(x,y0,y1,y2,y3)],[0,0,6,PI/4],0,10,100)
PlotData(m[1][0],m[1][1])
