
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
In the Cartesian coordinate system, O is the origin. It is known that $\overrightarrow {p}=(-1, 2)$, A(8, 0), B(n, t), and C(ksinθ, t), where $0 \leq \theta \leq \frac{\pi}{2}$  
(1) If $\overrightarrow {AB} \perp \overrightarrow {p}$ and $|\overrightarrow {AB}|= \sqrt {5}|\overrightarrow {OA}|$, find the vector $\overrightarrow {OB}$;  
(2) If vector $\overrightarrow {AC} \parallel \overrightarrow {p}$, when k is a constant greater than 4, tsinθ reaches its maximum value of 4, find the tangent of the angle between $\overrightarrow {OA}$ and $\overrightarrow {OC}$ at this time.

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