What is the range of \(\cosec \theta\)?
Answer and explanation
Correct answer: \(( -\infty,-1]\cup[1,\infty)\)
\(\cosec\theta=\frac{1}{\sin\theta}\). Since \(-1\leq\sin\theta\leq1\) and \(\sin\theta\neq0\), the value of \(\cosec\theta\) is either less than or equal to \(-1\), or greater than or equal to 1. At \(\sin\theta=-1\) and \(1\), we get \(\cosec\theta=-1\) and \(1\), so both endpoints are included. Option C incorrectly excludes these endpoints. Exam tip: for reciprocal trigonometric functions, check values for which the denominator becomes zero.
Frequently asked questions
What is the correct answer to this question?
\(( -\infty,-1]\cup[1,\infty)\)
Why is this the correct answer?
\(\cosec\theta=\frac{1}{\sin\theta}\). Since \(-1\leq\sin\theta\leq1\) and \(\sin\theta\neq0\), the value of \(\cosec\theta\) is either less than or equal to \(-1\), or greater than or equal to 1. At \(\sin\theta=-1\) and \(1\), we get \(\cosec\theta=-1\) and \(1\), so both endpoints are included. Option C incorrectly excludes these endpoints. Exam tip: for reciprocal trigonometric functions, check values for which the denominator becomes zero.
Which subject and chapter does this question cover?
This is a Class 12 Mathematics question. Chapter: Trigonometric Functions. Topic: Trigonometric functions and their properties.
