The principal solution of cos-1(-1/2) is - Mathematics and Statistics

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MCQ

The principal solution of `cos^-1(-1/2)` is :

Options

  • `pi/3`

  • `pi/6`

  • `(2pi)/3`

  • `(3pi)/2`

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Solution

The principal solution of `cos^-1(-1/2)= ` An angle in [0,π], whose cosine is -1/2

⇒ `cos^-1(-1/2) = pi - "cos"^-1 (1/2)`   .....[because cos-1 (-x) = π - cos x]

`= pi - pi/3 = (2pi)/3`

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2014-2015 (March)

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