
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
In a tetrahedron \( A B C D \) with all edges of equal length, \( E \) and \( F \) are the midpoints of \( A D \) and \( B C \) respectively. Connect \( A F \) and \( C E \).

(I) Find the angle between the skew lines \( A F \) and \( C E \).

(II) Find the angle between \( C D \) and the plane \( B C D \).

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