
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 function $f(x)=\sin x\cos x-\cos ^{2}x$.  
$(1)$ Find the interval where $f(x)$ is decreasing.  
$(2)$ Let the zeros of $f(x)$ on $(0,+\infty)$ be arranged in ascending order to form a sequence $\{a_{n}\}$. Find the sum of the first $10$ terms of $\{a_{n}\}$.

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