
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 $$a= \frac {1}{\pi } \int_{ -1 }^{ 1 }( \sqrt {1-x^{2}}+\sin x)dx$$, find the constant term in the expansion of the binomial $$(2x- \frac {a}{x^{2}})^{9}$$.

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