Cfrgtkky

I want to produce a figure like this:

with this code:

begin{tikzpicture}



draw (0,0) circle [radius=10.75cm];

draw (0,0) circle [radius=4.2cm];



begin{scope}[even odd rule]

 draw[fill=gray!20,thick] (0,0) circle [radius=8cm] circle [radius=6cm];

end{scope}







draw [fill=white] node (x25) {} (6.042,1.053) circle [radius=1.05cm];







draw [fill=white] (0.363,7.83) circle [radius=1.05cm] node[inner sep=2pt,circle,fill=black,pos=0.5] (x26) {};









draw [fill=white] (-6.04,-1.069) circle [radius=1.05cm] node[inner sep=2pt,circle,fill=black,pos=0.5] (x27) {};









draw [fill=white] (-0.35,-7.821) circle [radius=1.05cm] node[inner sep=2pt,circle,fill=black,pos=0.5] (x28) {};









draw (0,0) -- (x25) node[pos=0.5,fill=white,circle] {$r_1$};

draw (0,0) -- (x26) node[pos=0.4,fill=white,circle] {$r_2$};

draw (0,0) -- (x27) node[pos=0.5,fill=white,circle] {$r_3$};

draw (0,0) -- (x28) node[pos=0.4,fill=white,circle] {$r_4$};





draw (0,0) -- ++(3.5,0);



draw[->] (0:2.5cm) arc (0:9.893:2.5cm) node[pos=0.5,label={0:$varphi_1$}] {};

draw[->] (0:2.0cm) arc (0:87.347:2.0cm) node[pos=0.5,fill=white,circle] {$varphi_2$};

draw[->] (0:1.5cm) arc (0:190.0:1.5cm) node[pos=0.6,fill=white,circle] {$varphi_3$};

draw[->] (0:1cm) arc (0:267.37:1cm) node[pos=0.5,fill=white,circle] {$varphi_4$};





end{tikzpicture}

however I obtain only this:

The lines from the origin to the nodes x25 to x28 do not appear.

Any help?

The first node (x25) is placed at the origin (0,0) since you did not specify where it should be.
By moving its definition after the coordinate (6.042,1.053) it moves to where you want it to be.
I simply commented on the other parts of your useless code. But I didn't simplify your code.

Update: more explanations

Following @JohnKormylo's comment, I looked for the cause of this error and unless I'm mistaken, it's because the path is reduced to a single point, instead of two: the current point and the previous point.

Here is your reduced code to a minimum:

draw [fill=white] (0.363,7.83) circle [radius=1.05cm] node[pos=0.5] (x26) {};

Indeed, I am quoting page 151 of the manual:

path ... circle[< options >] ...; This command adds a circle to the
current path where the center of the circle is the current point by
default, but you can use the at option to change this. The new current
point of the path will be (typically just remain) the center of the
circle.

And the page 235 of the manual:

/tikz/pos=< fraction > (no default) When this option is given, the node is
not anchored on the last coordinate. Rather, it is anchored on some
point on the line from the previous coordinate to the current point.

documentclass{standalone}



usepackage{tikz}





begin{document}

begin{tikzpicture}



draw (0,0) circle [radius=10.75cm]node[draw,circle,inner sep=2pt,fill=black]{}; 

draw (0,0) circle [radius=4.2cm];



begin{scope}[even odd rule]

 draw[fill=gray!20,thick] (0,0) circle [radius=8cm] circle [radius=6cm];

end{scope}



draw [fill=white] (6.042,1.053) circle [radius=1.05cm]node[draw,circle,inner sep=2pt,fill=black] (x25) {} ;

draw [fill=white] (0.363,7.83) circle [radius=1.05cm] 

[inner sep=2pt,circle,fill=black

%,pos=0.5

] (x26) {};

draw [fill=white] (-6.04,-1.069) circle [radius=1.05cm] node

[inner sep=2pt,circle,fill=black

%,pos=0.5

]

 (x27) {};

draw [fill=white] (-0.35,-7.821) circle [radius=1.05cm] node

[inner sep=2pt,circle,fill=black

%,pos=0.5

] 

(x28) {};



draw (0,0) -- (x25) node[pos=0.5,fill=white,circle] {$r_1$};

draw (0,0) -- (x26) node[pos=0.4,fill=white,circle] {$r_2$};

draw (0,0) -- (x27) node[pos=0.5,fill=white,circle] {$r_3$};

draw (0,0) -- (x28) node[pos=0.4,fill=white,circle] {$r_4$};



draw (0,0) -- ++(3.5,0);



draw[->] (0:2.5cm) arc (0:9.893:2.5cm) node[pos=0.5,label={0:$varphi_1$}] {};

draw[->] (0:2.0cm) arc (0:87.347:2.0cm) node[pos=0.5,fill=white,circle] {$varphi_2$};

draw[->] (0:1.5cm) arc (0:190.0:1.5cm) node[pos=0.6,fill=white,circle] {$varphi_3$};

draw[->] (0:1cm) arc (0:267.37:1cm) node[pos=0.5,fill=white,circle] {$varphi_4$};



end{tikzpicture}

end{document}