Applications Of Derivatives Question 236

Question: The maximum value of exp $ (2+\sqrt{3}\cos x+\sin x) $ is

[AMU 1999]

Options:

A) $ \exp (2) $

B) $ \exp (2-\sqrt{3}) $

C) $ \exp (4) $

D) 1

Show Answer

Answer:

Correct Answer: C

Solution:

Let $ y=\exp (2+\sqrt{3}\cos x+\sin x) $

therefore $ {y}’=\exp (2+\sqrt{3}\cos x+\sin x),(-\sqrt{3}\sin x+\cos x) $
Now $ {y}’=0 $

therefore $ -\sqrt{3}\sin x+\cos x=0 $

therefore $ \sin ( x-\frac{\pi }{6} )=0 $

therefore $ x=\frac{\pi }{6} $
Now $ {y}’’ $ is -ve at $ x=\frac{\pi }{6} $
\Maximum value of
$ y=\exp ,( 2+\sqrt{3}( \frac{\sqrt{3}}{2} )+\frac{1}{2} ) $ = $ \exp (4) $ .