Q110 / 180 · KCET 2018 · Mathematics

If \( f(x)=|\cos x-\sin x| \), then \( f^{\prime}\left(\frac{\Pi}{6}\right) \) is equal to

  • Correct answer
    A
    \( -\frac{1}{2}(1+\sqrt{3}) \)
  • B
    \( \frac{1}{2}(1+\sqrt{3}) \)
  • C
    \( -\frac{1}{2}(1-\sqrt{3}) \)
  • D
    \( \frac{1}{2}(1-\sqrt{3}) \)

Solution

Given that, $f(x)=|\cos x-\sin x|$ So, $f^{\prime}(x)=-\sin x-\cos x$ At $x=\frac{\Pi}{6}$, we have $f^{\prime}\left(\frac{\Pi}{6}\right)=-\sin \left(\frac{\Pi}{6}\right)-\cos \left(\frac{\Pi}{6}\right)$ $=-\frac{1}{2}-\frac{\sqrt{3}}{2}=\frac{-1}{2}(1+\sqrt{3})$

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

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