Find the value equal to cos(cos^-1 cos(8pi/7) + tan^-1 tan (8pi/7))

coscos-1cos8π7+tan-1tan8π7Note: cos-1 cosθ=θ only when θ is in domain of cos inverse function. Same goes for tan inverse=coscos-1cosπ+π7+tan-1tanπ+π7Since cosπ+θ=-cos θ and tanπ+θ=tan θ=coscos-1-cosπ7+tan-1tanπ7Since cos-1-θ=π- cos-1θ=cosπ-cos-1cosπ7+tan-1tanπ7=cosπ-π7+π7=cos π=-1

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