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CUET · MATHS · PYQ PAPER 2025

The function \(f: R \rightarrow[-1,1]\) defined by f(x) = cos x is:

  1. A one-one but not onto
  2. B onto but not one-one
  3. C Both one-one and onto
  4. D Neither one-one nor onto
Verified Solution

Answer & Solution

Correct Answer

(B) onto but not one-one

Step-by-step Solution

Detailed explanation

\(f(x_1) = f(x_2) \Rightarrow \cos x_1 = \cos x_2\). E.g., \(\cos 0 = 1, \cos 2\pi = 1\), but \(0 \neq 2\pi\). Not one-one. Range of \(\cos x\) for \(x \in R\) is \([-1,1]\). Codomain is \([-1,1]\). Range = Codomain. Onto. Onto but not one-one.
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