
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 the function $f(x)=2\sin\left(x+ \frac {\pi}{6}\right)-2\cos x$, $x\in\left[\frac {\pi}{2},\pi\right]$.  
(1) If $\sin x= \frac {4}{5}$, find the value of the function $f(x)$.  
(2) Determine the range of the function $f(x)$.

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