
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
In $\triangle DEF$, $DE = EF = 31$, and $DF = 40$. Calculate the area of $\triangle DEF$.
A) 450
B) 474
C) 500
D) 520
E) 550

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