
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
In $\triangle ABC$, the sides opposite to angles $A$, $B$, and $C$ are $a$, $b$, and $c$ respectively. It is given that $b\sin A=3c\sin B$, $a=3$, and $\cos B= \frac {2}{3}$.  
$(1)$ Find the value of $b$;  
$(2)$ Find the value of $\sin (2B- \frac {\pi}{3})$.

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