GATE Mechanical 2016 Set 2 | GA | Question: 10

Question

Which of the following curves represents the function $ln(|e^{[|\sin(|x|)]}|)$ for $\mid x\mid< 2\pi$? Here, $x$ represents the abscissa and $y$ represents the ordinate.

• A.
• B.
• C.
• D.

Comments

@makhdoom ghaya small typo in the question . Please correct it. I think you forgot to put right side mod symbol.

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Answer is graph of $\left | sin(\left |x \right |) \right |$. Because $ e^{x} $ will never be negative so mod could be removed.

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answer is c by transformation of graphs

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Put X= -π/2 then option B & Option D eliminated.

Put X=3π/2 then Option A eliminated.

So, Option  C is answer.

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we know the property ln(e^x)=x

so in the given question the given graph will be same as graph of |sinx|

https://www.mathway.com/popular-problems/Precalculus/454635

option c is graph of |sinx|

Answer 1

$f(x) = \large \ln \left( |e^{\left [ \;\; |{\color{blue}{\sin}} \left ( {\color{red}{|x|}} \right ) | \;\; \right ]}| \right )$

$1. \qquad {\color{red}{\bf |x|}}\rightarrow \;\; f(x)\;\;\; \text{is Even }\rightarrow \quad \text{option b not possible}$

$2. \qquad m = |\;{\color{blue}{\sin}} \left ( {\color{red}{\bf |x|}} \right ) | \;\; \geq \;\; 0 \quad \rightarrow {\color{blue}{e^{\bf m} \;\; \geq \;\; 1}}$

$3.\Rightarrow f(x) = \ln\left ( | \color{blue}{e^{\bf m}}| \right ) = \ln\left ( \color{blue}{e^{\bf m}}\right ) \geq 0 \quad \left \{ \text{from 2} \right\} \;\; \rightarrow \text{option a not possible}$

$4. \text{ and } f(x)_{x=0} = 0 \;\; \rightarrow \text{option d not possible}$

$\Rightarrow \text{answer C}$

Comments

But option b can be eliminated at 3π/2

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Option b can be eliminated through nature 1 as it is not symmetric to the y-axis. It is symmetric to the origin.

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Also at x = 3π/2, y = 1. So option C) answer, all other eliminated.

Answer 2

Function Y value will be positive only as Mod is given , A B eliminated now sinPi=0 D eliminated so C is answer