
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 sets $A=\{x|2\leqslant x\leqslant 8\}$, $B=\{x|1 \lt x \lt 6\}$, $C=\{x|x \gt a\}$, $U=R$.  
$(1)$ Find $A\cup B$, $(\complement _{U}A)\cap B$;  
$(2)$ If $A\cap C\neq \varnothing$, find the range of $a$.

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