
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given that \( F_{1} \) and \( F_{2} \) are the left and right foci of the hyperbola \( C: \frac{x^{2}}{a^{2}} - \frac{y^{2}}{b^{2}} = 1 \, (a > 0, b > 0) \), and that the circle with diameter \( F_{1}F_{2} \) intersects the hyperbola \( C \) at point \( P \) in the second quadrant, if the eccentricity of the hyperbola is 5, find the value of \( \cos \angle P F_{2} F_{1} \).

Present the answer in LaTex format: \boxed{Your answer}
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