
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
A new operation "*" between plane vectors is defined as follows: for any $$\overrightarrow {a}=(m，n)$$ and $$\overrightarrow {b}=(p，q)$$, let $$\overrightarrow {a}* \overrightarrow {b}=mq-np$$.
Give the following four propositions:
① If $$\overrightarrow {a}$$ and $$\overrightarrow {b}$$ are collinear, then $$\overrightarrow {a}* \overrightarrow {b}=0$$;
② $$\overrightarrow {a}* \overrightarrow {b}= \overrightarrow {b}* \overrightarrow {a}$$;
③ For any λ∈R, $$(λ \overrightarrow {a})* \overrightarrow {b}=λ( \overrightarrow {a}* \overrightarrow {b})$$;
④ $$( \overrightarrow {a}* \overrightarrow {b})^{2}+( \overrightarrow {a}\cdot \overrightarrow {b})^{2}=| \overrightarrow {a}|^{2}\cdot | \overrightarrow {b}|^{2}$$ (Note: Here $$\overrightarrow {a}\cdot \overrightarrow {b}$$ refers to the dot product of $$\overrightarrow {a}$$ and $$\overrightarrow {b}$$).
The sequence numbers of all true propositions are ________.

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