
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 that $0 < α < \frac{π}{2}$, and $\cos (2π-α)- \sin (π-α)=- \frac{ \sqrt {5}}{5}$,
(1) Find the value of $\sin α+ \cos α$;
(2) Find the value of $\frac{\cos ^{2}( \frac {3π}{2}+α)+2\cos α\cos ( \frac {π}{2}-α)}{1+\sin ^{2}( \frac {π}{2}-α)}$.

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