Principal values worked in the chapter
Exercise and reference answers
- Questions
- Question
- Principal value of sin⁻¹(1/√2)
- Choices
- π/3
- π/6
- π/4
- Correct choice
- π/4
- Question
- Principal value of cot⁻¹(−1/√3)
- Choices
- 2π/3
- −π/3
- π/3
- Correct choice
- 2π/3
- Question
- Why is cot⁻¹(−1/√3) not −π/3?
- Choices
- cot(−π/3) is undefined
- −π/3 is outside (0, π)
- −π/3 is not a real number
- Correct choice
- −π/3 is outside (0, π)
Explanation
Both values are computed in full in your syllabus Examples 1 and 2: sin⁻¹(1/√2) = π/4 because sin(π/4) = 1/√2 and π/4 lies in [−π/2, π/2]
cot⁻¹(−1/√3) = 2π/3 because cot(2π/3) = −1/√3 and 2π/3 lies in (0, π). Source: syllabus Maths Part I, Ch 2 Inverse Trigonometric Functions.
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