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Evaluate each of the following:
cos–1(cos 4)
cos–1(cos x) = x
Provided x ϵ [0,π] ≈ [0,3.14]
And in our equation x is 4 which does not lie in the above range.
We know cos[2π – x] = cos[x]
∴ cos(2π – 4) = cos(4)
Also 2π–4 belongs in [0,π]
∴ cos–1(cos 4) = 2π–4