Q71 / 180 · KCET 2025 · Mathematics

Let the functions " f " and " g " be $\mathrm{f}:\left[0, \frac{\pi}{2}\right] \rightarrow \mathrm{R}$ given by $\mathrm{f}(\mathrm{x})=\sin \mathrm{x}$ and $\mathrm{g}:\left[0, \frac{\pi}{2}\right] \rightarrow \mathrm{R}$ given by $g(x)=\cos x$, where $R$ is the set of real numbers Consider the following statements: Statement (I): f and g are one-one Statement (II): $\mathrm{f}+\mathrm{g}$ is one-one Which of the following is correct?

  • Correct answer
    A
    Statement (I) is true, statement (II) is false
  • B
    Statement (I) is false, statement (II) is true
  • C
    Both statements (I) and (I) are true
  • D
    Both statements (I) and (II) are false

Solution

$\begin{aligned} & \mathrm{f}: \text { one }- \text { one }\left[0, \frac{\pi}{2}\right] \rightarrow \text { R.f }(\mathrm{x})=\sin \mathrm{x} \\ & \mathrm{~g}: \text { one }- \text { one }\left[0, \frac{\pi}{2}\right] \rightarrow \text { R.f }(\mathrm{x})=\cos \mathrm{x} \end{aligned}$ Statement I is true $\begin{aligned} & (\mathrm{f}+\mathrm{g}):\left[0, \frac{\pi}{2}\right] \rightarrow \mathrm{R} \\ & \mathrm{f}+\mathrm{g}(\mathrm{x})=\sin \mathrm{x}+\cos \mathrm{x} \\ & \left.\begin{array}{l} \mathrm({f}+\mathrm{g})(0)=0 \\ (\mathrm{f}+\mathrm{g})(\pi / 2)=0 \end{array}\right\} \Rightarrow \mathrm{f}+\mathrm{g} \text { is not one }- \text { one } \end{aligned}$

Hence, the correct answer is option: 'A'.

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