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

Misc. 1 - Chapter 2 Class 12 Inverse Trigonometric Functions - Part 2

  1. Chapter 2 Class 12 Inverse Trigonometric Functions (Term 1)
  2. Serial order wise

Transcript

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°) But, Range of cos−1 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 (𝜋/6) ∴ y = 𝝅/𝟔 Which is in the range of cos-1 i.e. [0, π] Hence , cos −1 (cos 13π/6 " " ) = 𝝅/𝟔 (As cos (360 + θ) = cos θ)

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.