
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
The cosine of the angle between the skew lines \(AB\) and \(CD\) is \(\frac{\sqrt{35}}{10}\). Points \(E\) and \(F\) are the midpoints of the segments \(AB\) and \(CD\) respectively, and the line \(EF\) is perpendicular to the lines \(AB\) and \(CD\). Find the angle \( \angle ACB \) given that \(AB=2\sqrt{5}\), \(CD=2\sqrt{7}\), and \(EF=\sqrt{13}\).

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