
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 three points in space $A(-2,0,2)$, $B(-1,1,2)$, $C(-3,0,4)$, let $\overrightarrow{a}=\overrightarrow{AB}$, $\overrightarrow{b}=\overrightarrow{AC}$.  
$(1)$ Find the cosine value of the angle between $\overrightarrow{a}$ and $\overrightarrow{b}$.  
$(2)$ If the angle between $k\overrightarrow{a}+\overrightarrow{b}$ and $k\overrightarrow{a}-2\overrightarrow{b}$ is obtuse, find the range of values for $k$.

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