
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 $\overrightarrow{m}=(\cos x+ \sqrt {3}\sin x,1)$ and $\overrightarrow{n}=(2\cos x,a)(a∈R)$, the minimum value of the function $f(x)= \overrightarrow{m}\cdot \overrightarrow{n}$ on $R$ is $2$.
(I) Find the value of $a$ and the interval where $f(x)$ is monotonically decreasing;
(II) First shift the graph of the function $y=f(x)$ to the right by $\frac {π}{6}$ units, then shrink the x-coordinates of all points on the resulting graph to $\frac {1}{2}$ of their original length (the y-coordinates remain unchanged) to obtain the graph of the function $y=g(x)$. Find the sum of all zeros of the function $t(x)=g(x)-5$ in the interval $\[- \frac {π}{2},0\]$

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