
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 the parametric equations of line $l$ as $\begin{cases} x= \frac {1}{2}t \\ y= \frac { \sqrt {3}}{2}t\end{cases}$ (where $t$ is the parameter), and the polar equation of circle $C$ is $\rho=4\sin \theta$. Establish a Cartesian coordinate system with the pole as the origin and the polar axis as the positive direction of the $x$-axis,  
(Ⅰ) Write the polar equation of line $l$;  
(Ⅱ) Find the length of the chord cut off from circle $C$ by line $l$.

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