This question already has an answer here:

If circle and line is a draw command as below, is it possible to get intersection? for this example, the C point now is hardcoded.

 \coordinate (O) at (0,0);
 \coordinate (A) at (1,0);
 \coordinate (B) at (1,1.732);
 \draw[->] (0,0) -- (2,0);
 \draw[->] (0,0) -- (0,2);
 \draw (A) circle (1);
 \draw (A) -- (1,2);
 \draw (O) -- (B);
 \coordinate (C) at (0.5,0.861);//fix me with intersection of circle and line
 \draw (A) -- (C); 
 % annotation
 \draw[fill=red] (O) circle (1pt)  node[below left=0 of O] {O};
 \draw[fill=red] (A) circle (1pt)  node[below right=0 of A] {A};
 \draw[fill=red] (B) circle (1pt)  node[above right=0 of B] {B};
 \draw[fill=red] (C) circle (1pt)  node[above left=0 of C] {C};


enter image description here

marked as duplicate by Stefan Pinnow, Andrew, Werner, Zarko tikz-pgf Nov 14 '16 at 22:28

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  • @GroCo So I should not use draw command but use node command? Is it exactly the same to replace draw with node? – lucky1928 Nov 14 '16 at 21:10

Consider using the tkz-euclide package. There is a command to find the intersection point of a line and a circle.

The following is from highschoolmathandchess.com:

tkzInterLC(A,B)(C,D) where (A,B) are points on the line and (C,D) is the center of a circle and a point on the circle.

  • The cited domain is for sale, at present... – kebs May 9 at 12:29

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