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MHT CET · Maths · Application of Derivatives

If the normal to the curve \(y=\mathrm{f}(x)\) at the point (3,4) makes an angle of \(\left(\frac{3 \pi}{4}\right)\) with the positive X -axis, then the value of \(\mathrm{f}^{\prime}(3)\) is

  1. A -1
  2. B \(-\frac{3}{4}\)
  3. C \(\frac{4}{3}\)
  4. D 1
Verified Solution

Answer & Solution

Correct Answer

(D) 1

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \text { Slope of the normal }=\frac{-1}{\frac{\mathrm{~d} y}{\mathrm{~d} x}} \\ & \Rightarrow \tan \frac{3 \pi}{4}=\frac{-1}{\left(\frac{\mathrm{~d} y}{\mathrm{~d} x}\right)_{(3,4)}} \\ & \Rightarrow\left(\frac{\mathrm{d} y}{\mathrm{~d} x}\right)_{(3,4)}=\mathrm{i} \\ & \Rightarrow \mathrm{f}^{\prime}(3)=1\end{aligned}\)