
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 the function $f(x)=2\cos ^{2} \frac{x}{2}- \sqrt {3}\sin x$.
(I) Find the smallest positive period and the range of the function;
(II) If $a$ is an angle in the second quadrant and $f(a- \frac {π}{3})= \frac {1}{3}$, find the value of $\frac {\cos 2a}{1-\tan a}$.

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