
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
(I) Given that $α$ and $β$ are acute angles, and $α+β= \frac {π}{4}$, find the value of $(1+\tan α)(1+\tan β)$.

(II) Given that $\frac {π}{2} < β < α < \frac {3π}{4}$, and $\cos (α-β)= \frac {12}{13}$, $\sin (α+β)=- \frac {3}{5}$, find the value of $\sin 2α$.

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