function graf3D
k=input('Zadej konec intervalu: ');
if((k>=20)&&(k<=100))
    t=0:0.1:k;
    x=sin(t);
    y=cos(t);
    z=t;
    plot3(x,y,z,'m')
    xlabel('x')
    ylabel('y')
    zlabel('z')
else
    disp('nekreslim')
end
end

