Recent questions tagged complex-analysis

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GATE EC 2021 | Question: 26
Consider the integral $\oint _{c}\frac{sin\left ( x \right )}{x^{2}\left ( x^{2}+4 \right )}dx$ where $C$ is a counter-clockwise oriented circle defined as $\left | x-i \right |=2$. The value of the integral is $-\frac{\pi }{8}\sin\left ( 2i \right )$ $\frac{\pi }{8}\sin\left ( 2i \right )$ $-\frac{\pi }{4}\sin\left ( 2i \right )$ $\frac{\pi }{4}\sin\left ( 2i \right )$

asked Feb 20 in Complex Analysis by Arjun (4.4k points) | 68 views

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GATE ECE 2019 | Question: 1
Which one of the following functions is analytic over the entire complex plane? $\ln(z)$ $e^{1/z}$ $\frac{1}{1-z}$ $\cos(z)$

asked Feb 12, 2019 in Complex Analysis by Arjun (4.4k points) | 216 views

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GATE ECE 2016 Set 3 | Question: 2
For $f(z)= \large\frac{\sin(z)}{z^2}$, the residue of the pole at $z = 0$ is _______

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 20 views

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GATE ECE 2016 Set 3 | Question: 29
The values of the integral $\large\frac{1}{2\pi j}\oint_c\frac{e^z}{(z-2)} \small dz$ along a closed contour $c$ in anti-clockwise direction for the point $z_0=2$ inside the contour $c$, and the point $z_0=2$ outside the contour $c$, respectively,are $(i)2.72, \: (ii) 0$ $(i)7.39, \: (ii) 0$ $(i)0, \: (ii) 2.72$ $(i)0, \: (ii) 7.39$

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 12 views

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GATE ECE 2016 Set 2 | Question: 2
Consider the complex valued function $f(z)=2z^{3}+b\mid z \mid^{3}$ where $z$ is a complex variable. The value of $b$ for which function $f(z)$ is analytic is _________

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 17 views

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GATE ECE 2016 Set 2 | Question: 27
Suppose $C$ is the closed curve defined as the circle $x^{2}+y^{2}=1$ with $C$ oreinted anti-clockwise. The value of $\oint$ ( $xy^{2}$ $dx$ + $ x^{2}y$ $dy$ )over the curve $C$ equals _________

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 12 views

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GATE ECE 2016 Set 1 | Question: 6
Which one of the following is an eigen function of the class of all continuous-time, linear, time-invariant systems ($u(t)$ denotes the unit-step function)? $e^{j\omega_0t}u(t)$ $\cos(\omega_0t)$ $e^{j\omega_0t}$ $\sin(\omega_0t)$

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 17 views

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GATE ECE 2016 Set 1 | Question: 28
In the following integral, the contour $C$ encloses the points $2 \pi j$ and $- 2\pi j$ $-\frac{1}{2\pi}\oint_C\frac{\sin z}{(z-2\pi j)^3} \,dz$ The value of the integral is _________

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 19 views

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GATE ECE 2015 Set 3 | Question: 51
The complex envelope of the bandpass signal $x(t)=-\sqrt{2}\left(\dfrac{\sin (\pi t/5)}{\pi t/5}\right)\sin (\pi t - \dfrac{\pi}{4}),$ centered about $f=\dfrac{1}{2}\:Hz,$ is $\left(\dfrac{\sin (\pi t/5)}{\pi t/5}\right)e^{j\dfrac{\pi}{4}}$ ... $\sqrt{2} \left(\dfrac{\sin (\pi t/5)}{\pi t/5}\right)e^{-j\dfrac{\pi}{4}}$

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 11 views

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GATE ECE 2015 Set 2 | Question: 3
Let $f(z)=\dfrac{az+b}{cz+d}.$ If $f(z_{1})=f(z_{2})$ for all $z_{1}\neq z_{2},a=2,b=4$ and $c=5,$ then $d$ should be equal to ________.

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 11 views

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GATE ECE 2015 Set 2 | Question: 28
If $C$ denotes the counterclockwise unit circle, the value of the contour integral $\dfrac{1}{2\pi j}\oint_{C} Re\{z\}dz$ is __________.

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 16 views

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GATE ECE 2015 Set 1 | Question: 4
Let $z=x+iy$ be a complex variable. Consider that contour integration is performed along the unit circle in anticlockwise direction. Which one of the following statements is NOT TRUE? The residue of $\frac{z}{z^2-1}$ at $z=1$ is $1/2$ $\oint_C z^2 dz=0$ $\frac{1}{2 \pi i} \oint_C \frac{1}{z} dz =1$ $\overline{z}$ (complex conjugate of $z$ is an analytical function

asked Mar 28, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 19 views

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GATE ECE 2014 Set 2 | Question: 27
The real part of an analytic function $f(z)$ where $z = x + jy$ is given by $e^{-y} \cos(x)$. The imaginary part of $f(z)$ is $e^{y} \cos( x )$ $e^{-y} \sin( x )$ $-e^{y} \sin ( x )$ $-e^{-y} \sin (x )$

asked Mar 26, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 33 views

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GATE ECE 2014 Set 1 | Question: 3
$C$ is a closed path in the $z$-plane given by $\mid z \mid = 3.$ The value of the integral $\displaystyle{}\oint_{C}\bigg(\dfrac{z^{2}-z+4j}{z+2j}\bigg)dz$ is $-4\pi(1+j2)$ $4\pi(3-j2)$ $-4\pi(3+j2)$ $4\pi(1-j2)$

asked Mar 26, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 16 views

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GATE ECE 2014 Set 1 | Question: 27
For a function $g(t),$ it is given that $\int_{- \infty}^{ + \infty} g(t)e^{-j\omega t}\:dt = \omega e^{-2\omega^{2}}$ for any real value $\omega.$ If $y(t) = \int_{- \infty}^{t}\:g(\tau)\:d\tau,$ then $\int_{- \infty}^{ + \infty}y(t)dt$ is $0$ $-j$ $-\frac{j}{2}$ $\frac{j}{2}$

asked Mar 26, 2018 in Complex Analysis by Milicevic3306 (15.8k points) | 15 views

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GATE ECE 2018 | Question: 51
The contour $C$ given below is on the complex plane $z=x+j y,$ where $j=\sqrt{-1}.$ The value of the integral $\displaystyle{}\dfrac{1}{\pi j}\oint _{C}\dfrac{dz}{z^{2}-1}$ is _______.

asked Feb 19, 2018 in Complex Analysis by gatecse (1.5k points) | 155 views

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GATE ECE 2017 Set 2 | Question: 4
The residues of a function $f(z)=\frac1{(z-4)(z+1)^3 }$ are $\frac{-1}{27}$ and $\frac{-1}{125} \\$ $\frac{1}{125}$ and $\frac{-1}{125} \\$ $\frac{-1}{27}$ and $\frac{1}{5} \\$ $\frac{1}{125}$and $\frac{-1}{5}$

asked Nov 23, 2017 in Complex Analysis by admin (2.8k points) | 27 views

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GATE ECE 2017 Set 1 | Question: 48
Which one of the following options correctly describes the locations of the roots of the equation $s^{4}+s^{2}+1=0$ on the complex plane? Four left half plane(LHP) roots One right half plane(RHP) root,one LHP root and two roots on the imaginary axis Two RHP roots and two LHP roots All four roots are on the imaginary axis

asked Nov 17, 2017 in Complex Analysis by admin (2.8k points) | 50 views

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GATE ECE 2017 Set 1 | Question: 28
Let $I=\int_{c}\left ( 2zdx+2ydy+2xdx \right )$ where $x,y,z$ are real, and let $C$ be the straight line segment from point $A:(0,2,1)$ to point $B:(4,1,-1)$.The value of $I$ is ____________.

asked Nov 17, 2017 in Complex Analysis by admin (2.8k points) | 62 views