
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 that point $A(-2,α)$ lies on the terminal side of angle $α$ and $\sin α=- \dfrac{ \sqrt{5}}{5}$.

(1) Find the values of $α$, $\cos α$, and $\tan α$.

(2) Find the value of $\dfrac{\cos ( \dfrac{π}{2}+α)\sin (-π-α)}{\cos ( \dfrac{11π}{2}-α)\sin ( \dfrac{9π}{2}+α)}$.

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