question: The graph shows an angle $a$ in standard position with its terminal side intersecting the circle at $P\left(\frac{20}{29},-\frac{21}{29}\right)$. The center of the circle is the origin and the radius of the circle is 1.
  
  Find the value of $\cos a$.
  
query_wo: Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
  Question: The graph shows an angle $a$ in standard position with its terminal side intersecting the circle at $P\left(\frac{20}{29},-\frac{21}{29}\right)$. The center of the circle is the origin and the radius of the circle is 1.
  
  Find the value of $\cos a$.
  
query_cot: Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
  Question: The graph shows an angle $a$ in standard position with its terminal side intersecting the circle at $P\left(\frac{20}{29},-\frac{21}{29}\right)$. The center of the circle is the origin and the radius of the circle is 1.
  
  Find the value of $\cos a$.
  
question_for_eval: The graph shows an angle $a$ in standard position with its terminal side intersecting the circle at $P\left(\frac{20}{29},-\frac{21}{29}\right)$. The center of the circle is the origin and the radius of the circle is 1.
  
  Find the value of $\cos a$.
  