
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 tetrahedron \(PQRS\),
\[\angle PRS = \angle PSQ = \angle QRS = 90^\circ.\]
Also, let \(a = \sin \angle PQS\) and \(b = \sin \angle PRQ\). Express \(\cos \angle PQRS\) in terms of \(a\) and \(b\).

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