Evaluate each of the following:

The value of cos is

Now,

∴ The question becomes cos^{–1}()

Let cos^{–1} ^{=} y

⇒ cos y =

= –cos

= cos

⇒ cos

The range of principal value of cos^{–1} is [0,π] and cos

Therefore, the value of cos^{–1}(cos) is.

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