title: Python can't define tuples in a function
body: <p>For some reason in python everytime I try to define tuples in a function I get a syntax error. For example I have a function that adds vectors to the program, it looks like this:</p>
  
  <pre><code>def add_vectors((angle_1, l_1),(angle_2, l_2)):
      x=math.sin(angle1)*l_1+math.sin(angle2)*l_2
      y=math.cos(angle1)*l_1+math.cos(angle2)*l_2
  
      angle=0.5*math.pi-math.atan2(y, x)
      length=math.hypot(x, y)
      return (angle, length)
  </code></pre>
  
  <p>Which seems alright, but the interpretor says there is a syntax error and highlights the first bracket of the first tuple. I am using Python 3.2.3. What am I doing wrong?</p>