
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 point $G$ is the centroid of $\triangle ABC$, with the sides opposite to angles $A$, $B$, $C$ having lengths $a$, $b$, $c$ respectively, and it is known that $\frac{a}{5}\overrightarrow{GA} + \frac{b}{7}\overrightarrow{GB} + \frac{c}{8}\overrightarrow{GC} = \overrightarrow{0}$, then the measure of angle $B$ is \_\_\_\_\_\_.

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