
Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class
Finding principal value
Example 1 Important
Ex 2.1, 1
Ex 2.1, 3
Ex 2.1, 10 Important
Ex 2.1, 2
Ex 2.1, 5 Important
Ex 2.1, 9
Ex 2.1, 7 Important
Ex 2.1, 4 Important
Ex 2.1, 6
Ex 2.1, 8 Important
Example 2
Ex 2.2, 10
Example 6 Important
Ex 2.2, 8
Ex 2.2, 11
Misc 2 Important
Ex 2.2, 13 (MCQ) Important You are here
Misc 1
Ex 2.2, 14 (MCQ) Important
Ex 2.2, 15 (MCQ)
Ex 2.1, 12 Important
Ex 2.1, 14 (MCQ) Important
Ex 2.1, 11 Important
Last updated at May 29, 2023 by Teachoo
Ex 2.2, 19 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 (As cos (360° – θ) = cos θ)