GATE CSE
First time here? Checkout the FAQ!
x
+3 votes
277 views
asked in Calculus by Boss (6.8k points)   | 277 views

2 Answers

+9 votes
Best answer

$e^\sqrt{2}$ will be the highest value of the given expression.

$\frac{e^{\sin x}}{e^{\cos x}}$ can be written as $e^{\sin x - \cos x}$.

$e$ is a famous irrational constant that is used as base of natural logarithms, and its approximate value is $2.7183$, (which is of course greater than $1$).

So now we just have to maximize $(\sin x - \cos x)$ to find the maximum value of given expression.


Clearly $\sin x$ and $\cos x$ are differentiable functions, hence their difference $(\sin x - \cos x)$ is also differentiable.

So we can differentiate $\sin x - \cos x$ to find its maximum value.

Solution of the equation $\frac{d}{dx}(\sin x - \cos x) = 0$ will give us the points where $\sin x - \cos x$ will attain its maximum value.

On differentiating $(\sin x - \cos x)$ with respect to $x$, we get $\cos x + \sin x$.

Putting $\cos x + \sin x = 0$ and simplifying we get 

$\tan x = -1$

This equation has infinitely many solutions.

One of them is $x = \frac{3\pi}{4}$$x = \frac{3\pi}{4} \text{radians or 135 degrees}$ .

$\sin \left(\frac{3\pi}{4} \right ) = \frac{1}{\sqrt2} \text{ and }\cos \left(\frac{3\pi}{4} \right ) = \frac{-1}{\sqrt2}$.

Putting these values in $e^{\sin x - \cos x}$, we get $e^{\sqrt2}$ or $e^{1.414}$.

 

answered by Veteran (12.7k points)  
selected by
0 votes

Say,Y=esinx / ecosx 

=>log Y =log(esinx / ecosx)

=>log Y =log esinx - log ecosx

              =sinx - cosx

           =1

 log Y =log e

      Y=e

answered by Veteran (53.1k points)  
sin x - cos x = 1?

what is the error if x=⊼/2

then sin⊼/2 -cos⊼/2=1 . isnot it?

yes, but that need not be maximum as cos x can go negative. $\frac {1}{\sqrt 2} - (-\frac{1}{\sqrt 2})$ gives the maximum value here.


Top Users Apr 2017
  1. akash.dinkar12

    3508 Points

  2. Divya Bharti

    2542 Points

  3. Deepthi_ts

    2040 Points

  4. rude

    1966 Points

  5. Tesla!

    1768 Points

  6. Shubham Sharma 2

    1610 Points

  7. Debashish Deka

    1588 Points

  8. Arunav Khare

    1454 Points

  9. Kapil

    1424 Points

  10. Arjun

    1420 Points

Monthly Topper: Rs. 500 gift card

22,076 questions
28,040 answers
63,230 comments
24,135 users