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Question
Evaluate the following:
`cos^-1{cos (5pi)/4}`
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Solution
We know
`cos^-1(costheta)=thetaif 0<=theta<=pi`
We have
`cos^-1{cos (5pi)/4}=cos^-1{cos(2pi-(3pi)/4)}`
`=cos^-1{cos((3pi)/4)}`
`=(3pi)/4`
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