
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 $f(x)=A\sin (\omega x+\varphi)$ ($A > 0$, $\omega > 0$, $|\varphi| < \pi$), within the same period, when $x= \frac {\pi}{2}$, $f(x)$ reaches its maximum value of $3$, and when $x=- \frac {3\pi}{2}$, $f(x)$ reaches its minimum value of $-3$.  
(Ⅰ) Find the analytical expression of the function $f(x)$.  
(Ⅱ) Find the interval of monotonic decrease for the function $f(x)$.

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