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 answerAStatement (I) is true, statement (II) is false
- BStatement (I) is false, statement (II) is true
- CBoth statements (I) and (I) are true
- DBoth 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'.