Misc 1 - Find cos-1 (cos 13pi/6) - Chapter 2 Class 12 NCERT - Miscellaneous

  1. Chapter 2 Class 12 Inverse Trigonometric Functions
  2. Serial order wise
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Misc 1 Find the value of cos-1 (cos⁡〖13π/6〗 )  Let y = cos-1(cos 13π/6) cos y = cos 13π/6 cos y = cos (390°) We know that range of principal value of cos is [0,π] i.e. [0° ,180°] Hence y = 390° not possible Now, cos y = cos (390°) cos y = cos (360° + 30°) cos y = cos (30°) cos y = cos (30 × 𝜋/180) cos y = cos (𝜋/6) y = 𝜋/6 Which is in the range of principal value of cos-1 i.e. [0,π] Hence , cos −1 (cos 13π/6 " " ) = y = 𝜋/6

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Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.