
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
Let the two foci of the hyperbola $\frac {y^{2}}{a^{2}}- \frac {x^{2}}{3}=1$ be $F_{1}$ and $F_{2}$, with an eccentricity of $2$.
(Ⅰ) Find the equations of the asymptotes $l_{1}$ and $l_{2}$ of this hyperbola;
(Ⅱ) If $A$ and $B$ are points on $l_{1}$ and $l_{2}$ respectively, and $2|AB|=5|F_{1}F_{2}|$, find the equation of the trajectory of the midpoint $M$ of line segment $AB$, and describe what kind of curve this trajectory is.

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