
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 ellipse $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1 (a > b > 0)$, respectively, and $P$ is a point on the ellipse such that $PF_2$ is perpendicular to the $x$-axis, and $\sin \angle F_1PF_2 = \frac{4}{5}$, determine the eccentricity of the ellipse.

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