Ex 2.2, 13 (MCQ) - Chapter 2 Class 12 Inverse Trigonometric Functions (Important Question)

Last updated at April 16, 2024 by

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Ex 2.2, 13 Find the values of cos−1(cos 7π/6) is equal to (A) 7π/6 (B) 5𝜋/6 (C) 𝜋/3 (D) 𝜋/6 Let y = cos−1 (cos 7π/6) cos y = cos (7π/6) cos y = cos (210°) Since Range of of cos−1 is [0, π] i.e. [0° ,180°] Hence, y = 210° not possible Now, cos y = cos (210°) cos y = cos (360° – 150°) cos y = cos (150°) cos y = cos (𝟓𝝅/𝟔) Hence, y = 𝟓𝝅/𝟔 Which is in the range of principal value of cos-1 i.e. [0, π] Hence , cos −1 (cos 7π/6) = 5𝜋/6 Thus, option (B) is correct

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo