title: Difficulty in writing programs with MATLAB
body: <p>I am going to calculate the product</p>
  
  <pre><code>acc = 1.44e-10;
  a   = 1.732*acc;    
  a1  = (a/2) * [sqrt(3), -1, 0];
  a2  = (a/2) * [sqrt(3), 1, 0];
  coordinates = [4.45714 0 0; %B
                 2.22857 0 0.46152]; %A
  R1 = coordinates(2, :)-coordinates(1,:);
  R2 = R1 + a1;
  R3 = R1 + a2;
  R  = [R1' R2' R3'];
  n  = dot(R,[ 0 0 1])/norm(R); 
  </code></pre>
  
  <p>But I always get this error</p>
  
  <p><code>A and B must be same size.</code></p>