Question:

Find the maximum value of $f(x) = sin(sinx)$ for all $x \in R$

Updated On: Jul 6, 2022
  • $-sin \,1$
  • $sin \,6$
  • $sin \,1$
  • $-sin \,3$
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The Correct Option is C

Solution and Explanation

We have $f(x) = sin\,(sin\,x)$, $x \in R$ Now, $-1 \le sin \,x \le 1$ for all $x \in R$ $\Rightarrow sin \left(-1\right) \le sin\left(sinx\right) \le sin \,1$ for all $x \in R$ [$\because sin\, x$ is an increasing function on $\left[-1,1 \right]$] $\Rightarrow - sin\, 1 \le f\left(x\right) \le sin\, 1$ for all $x \in R$ This shows that the maximum value of $f\left(x\right)$ is $sin \,1$.
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Concepts Used:

Application of Derivatives

Various Applications of Derivatives-

Rate of Change of Quantities:

If some other quantity ‘y’ causes some change in a quantity of surely ‘x’, in view of the fact that an equation of the form y = f(x) gets consistently pleased, i.e, ‘y’ is a function of ‘x’ then the rate of change of ‘y’ related to ‘x’ is to be given by 

\(\frac{\triangle y}{\triangle x}=\frac{y_2-y_1}{x_2-x_1}\)

This is also known to be as the Average Rate of Change.

Increasing and Decreasing Function:

Consider y = f(x) be a differentiable function (whose derivative exists at all points in the domain) in an interval x = (a,b).

  • If for any two points x1 and x2 in the interval x such a manner that x1 < x2, there holds an inequality f(x1) ≤ f(x2); then the function f(x) is known as increasing in this interval.
  • Likewise, if for any two points x1 and x2 in the interval x such a manner that x1 < x2, there holds an inequality f(x1) ≥ f(x2); then the function f(x) is known as decreasing in this interval.
  • The functions are commonly known as strictly increasing or decreasing functions, given the inequalities are strict: f(x1) < f(x2) for strictly increasing and f(x1) > f(x2) for strictly decreasing.

Read More: Application of Derivatives