
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
Suppose \( c = \frac{2\pi}{13} \). Evaluate the following expression:
\[
\frac{\sin 4c \cdot \sin 8c \cdot \sin 12c \cdot \sin 16c \cdot \sin 20c}{\sin c \cdot \sin 2c \cdot \sin 3c \cdot \sin 4c \cdot \sin 5c}
\]
A) \( 1 \)
B) \( \frac{1}{\sin \frac{2\pi}{13}} \)
C) \( \sin \frac{2\pi}{13} \)
D) \( \sin \frac{4\pi}{13} \)

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