
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
(1) Given vectors $\overrightarrow {a}$=(-2,-1) and $\overrightarrow {b}$=(λ,1), find the range of λ if the angle between $\overrightarrow {a}$ and $\overrightarrow {b}$ is obtuse.
(2) For the non-coplanar vectors $\overrightarrow {a}$, $\overrightarrow {b}$, and $\overrightarrow {c}$ where each pair of vectors forms an equal angle, if $| \overrightarrow {a}|=| \overrightarrow {b}|=2$ and $| \overrightarrow {c}|=1$, find $| \overrightarrow {a}+ \overrightarrow {b}+ \overrightarrow {c}|$.

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