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 sin^{-1} (cos π/9)

We know that cos θ = sin (π/2 – θ)

= sin^{-1} (sin (π/2 - π/9))

= sin^{-1} (sin 7π/18)

We know that sin^{-1} (sin θ) = θ

= 7π/18

∴ sin^{-1} (cos π/9) = 7π/18

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