
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 vectors $\overrightarrow {m}=(\cos\alpha- \frac { \sqrt {2}}{3}, -1)$, $\overrightarrow {n}=(\sin\alpha, 1)$, and $\overrightarrow {m}$ is collinear with $\overrightarrow {n}$, and $\alpha\in[-\pi,0]$.  
(Ⅰ) Find the value of $\sin\alpha+\cos\alpha$;  
(Ⅱ) Find the value of $\frac {\sin2\alpha}{\sin\alpha-\cos\alpha}$.

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