title: Theorem Proof Using Prolog
body: <p>How can I write theorem proofs using Prolog?</p>
  <p>I have tried to write it like this:</p>
  <pre><code>parallel(X,Y) :-
      perpendicular(X,Z),
      perpendicular(Y,Z),
      X \== Y,
      !.
  
  perpendicular(X,Y) :-
      perpendicular(X,Z),
      parallel(Z,Y),
      !.
  </code></pre>
  <p>Can you help me?</p>