CBSE (Science) Class 12CBSE
Share
Notifications

View all notifications
Books Shortlist
Your shortlist is empty

Solution for F(X) = 2sin X − X, − π 2 < < X < π 2 . - CBSE (Science) Class 12 - Mathematics

Login
Create free account


      Forgot password?

Question

f(x) = 2sin x\[-\] x, \[- \frac{\pi}{2} < \frac{<}{}x\frac{<}{}\frac{\pi}{2}\] .

Solution

\[\text { Given: } \hspace{0.167em} f\left( x \right) = 2 \sin x - x\]

\[ \Rightarrow f'\left( x \right) = 2 \cos x - 1\]

\[\text { For a local maximum or a local minimum, we must have }\]

\[ f'\left( x \right) = 0\]

\[ \Rightarrow 2 \cos x - 1 = 0\]

\[ \Rightarrow \cos x = \frac{1}{2}\]

\[ \Rightarrow x = \frac{\pi}{3} or \frac{- \pi}{3}\]

Sincef '(x) changes from positive to negative when x increases through \[\frac{\pi}{3}\] x = \[\frac{\pi}{3}\] is the point of local maxima.
The local maximum value of  f (x) at x = \[\frac{\pi}{3}\] is given by

\[2 \sin \left( \frac{\pi}{3} \right) - \frac{\pi}{3} = \sqrt{3} - \frac{\pi}{3}\]

Since f '(x) changes from negative to positive when x increases through

\[- \frac{\pi}{3}\] x = \[- \frac{\pi}{3}\] is the point of local minima.

The local minimum value of  f (x)  at x = \[- \frac{\pi}{3}\]  is given by 

\[2 \sin \left( \frac{- \pi}{3} \right) + \frac{\pi}{3} = \frac{\pi}{3} - \sqrt{3}\]

  Is there an error in this question or solution?

Video TutorialsVIEW ALL [1]

Solution F(X) = 2sin X − X, − π 2 < < X < π 2 . Concept: Graph of Maxima and Minima.
S
View in app×