
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 $α$ is in the interval $( \frac {π}{2}, π)$ and $sinα= \frac {4}{5}$,
(1) Calculate the value of $cos(α- \frac {π}{4})$;
(2) Calculate the value of $sin^2\frac{α}{2}+ \frac{sin4αcos2α}{1+cos4α}$.

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