Answer each of the following questions in one word or one sentence or as per exact requirement of the question:

Write the value of .

Given cos^{-1} (tan 3π/4)

= cos^{-1} (tan (π - π/4))

We know that tan (π – θ) = - tan θ

= cos^{-1} (-tan π/4)

= cos^{-1} (-1)

We know that cos^{-1} x = π

∴ cos^{-1} (tan 3π/4) = π

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