The principal value of cos⁻¹(cos 7π/6) is:
The principal value of cos⁻¹(cos 7π/6) is:
- A. 7π/6
- B. 5π/6
- C. π/6
- D. −π/6
Answer: B) 5π/6
Explanation: cos⁻¹(cos θ) = 2π − θ if θ ∈ [π, 2π]. 7π/6 ∈ [π, 2π]. So cos⁻¹(cos 7π/6) = 2π − 7π/6 = 5π/6.
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