
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 $\overrightarrow {a}$=(cosθ, sinθ) and $\overrightarrow {b}$=(2, -1),
(1) If $\overrightarrow {a}$ is perpendicular to $\overrightarrow {b}$, find the value of $\frac {sinθ-cosθ}{sin\theta +cos\theta }$;
(2) If $|\overrightarrow {a}-\overrightarrow {b}|=2$ and $θ∈(0, \frac {π}{2})$, find the value of $sin(θ+ \frac {π}{4})$.

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