All Exams Test series for 1 year @ ₹349 only
Question

Which of the following is correct about first and second derivatives at points P, Q and R for $f(x) = \sin(x)$ shown below?

The correct answer is

$ \frac{d^2f}{dx^2}|_P < 0; \frac{d^2f}{dx^2}|_Q = 0; \frac{d^2f}{dx^2}|_R > 0$

To solve this problem, we need to analyze the behavior of the first and second derivatives of the function \(f(x) = \sin(x)\) at the points P, Q, and R in the given plot.

Let's break down the problem step by step:

  1. Consider the first and second derivatives of \(f(x) = \sin(x)\):
    • The first derivative is \(\frac{df}{dx} = \cos(x)\).
    • The second derivative is \(\frac{d^2f}{dx^2} = -\sin(x)\).
  2. Evaluate the derivatives at point P (maximum point):
    • At a maximum point, the first derivative \(\frac{df}{dx} = 0\) (since the slope is horizontal).
    • The second derivative is negative, \(\frac{d^2f}{dx^2} < 0\), indicating a local maximum. This is consistent with option (C).
  3. Evaluate the derivatives at point Q (inflection point):
    • At point Q, the second derivative \(\frac{d^2f}{dx^2} = -\sin(x) = 0\), indicating an inflection point where the concavity changes. This matches option (C).
  4. Evaluate the derivatives at point R (minimum point):
    • At a minimum point, the first derivative \(\frac{df}{dx} = 0\) (slope is again horizontal).
    • The second derivative is positive, \(\frac{d^2f}{dx^2} > 0\), indicating a local minimum. This aligns with option (C).

Based on the analysis above, we conclude that the correct answer is option (C), which states:

\(\frac{d^2f}{dx^2}|_P < 0; \frac{d^2f}{dx^2}|_Q = 0; \frac{d^2f}{dx^2}|_R > 0\)

Was this answer helpful?

Important Questions from Calculus

  1. The ratio of volume to surface area of solid semi sphere is related to its radius through

  2. The value of \(\int^2_0\int^x_0y\ dy\ dx\)

  3. Find the slope of normal to the curve y = x2 + 7x at (1, 8).

  4. Find the equation of normal to the curve y = 4x - 3x2 at (2, -4).

  5. \(\mathop {\lim }\limits_{\theta \to \frac{\pi }{2}} \frac{{\log \left( {\theta - \frac{\pi }{2}} \right)}}{{\tan \theta }}\)
Need Expert Advice?

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App