
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 two triangles, one with sides length 15, 36, and 39, and another with sides length 40, 42, and 58. Check if both are right triangles. Assuming they are, find the angle between the sides of lengths 15 and 36 using the Law of Cosines if these two sides meet at a point A and form an angle $\theta$.
A) $45^\circ$
B) $60^\circ$
C) $90^\circ$
D) $30^\circ$

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