Recent questions tagged complex-variables

If $w=\log _{e} z=\log _{e}(x+i y)$, where $i=\sqrt{-1}$, then which one of the following statements is correct?$w$ is analytic everywhere except at $z=0$$w$ is non-analy...

If $C$ is the unit circle in the complex plane with its center at the origin, then the value of $n$ in the equation given below is _________ (rounded off to $1$ decimal ...

​​​​​Let $f(z)$ be an analytic function, where $z=x+i y$. If the real part of $f(z)$ is $\cosh x \cos y$, and the imaginary part of $f(z)$ is zero for $y=0$, then $f(z)$ ...

The value of $k$ that makes the complex-valued function$$f(z)=e^{-k x}(\cos 2 y-i \sin 2 y)$$analytic, where $z=x+i y$, is __________. (Answer in integer)

Given $z = x + iy, i = \sqrt{-1}$. $C$ is a circle of radius $2$ with the centre at the origin. If the contour $C$ is traversed anticlockwise, then the value of the integ...

The value of the integral $$\oint \left ( \frac{6z}{2z^{4} - 3z^{3} + 7z^{2} - 3z + 5 } \right )dz$$ evaluated over a counter-clockwise circular contour in the complex pl...

Value of $\left ( 1+i \right )^{8}$, where $i=\sqrt{-1}$, is equal to$4$$16$$4i$$16i$

Let $\text{C}$ represent the unit circle centered at origin in the complex plane, and complex variable, $z=x+iy$. The value of the contour integral $\oint _{C}\dfrac{\cos...

The function $f(z)$ of complex variable $z=x+iy$, where $i=\sqrt{-1}$, is given as $f(z)=(x^3-3xy^2)+i \: v(x,y)$. For this function to be analytic, $v(x,y)$ should be$(3...

Which of the following function $f(z)$, of the complex variable $z,$ is NOT analytic at all the points of the complex plane?$f\left ( z \right )=z^{2}$$f\left ( z \right ...

An analytic function of a complex variable $z=x + iy \left ( i=\sqrt{-1} \right )$ is defined as$$f\left ( z \right )=x^{2}-y^{2}+i\psi \left ( x,y \right ),$$where $\psi...

Let $z$ be a complex variable. For a counter-clockwise integration around a unit circle $C$, centered at origin, $$\oint_C \frac{1}{5z-4} dz=A \pi i$$, the value of $A$ i...

$F(z)$ is a function of the complex variable $z=x+iy$ given by $F(z)+ i \: z + k \: Re(z) + i \: Im(z)$. For what value of $k$ will $F(z)$ satisfy the Cauchy-Riemann equa...

A function of the complex variable $z= x+iy$, is given as $f(x,y) =u(x,y) +iv(x,y)$ , where $u(x,y) = 2kxy$ and $ v(x,y) =x^2 −y^2$. The value of $k$, for which the funct...

$f(z)=u(x,y)+iv(x,y)$ is an analytic function of complex variable $z=x+iy$ where $i=\sqrt{-1}$. If $u(x,y)$=$2xy$ , then $v(x,y)$ may be expressed as$-x^2 + y^2 + $ const...

Given two complex numbers $z_1=5+(5\sqrt{3})i$ and $z_2=\dfrac{2}{\sqrt{3}}+2i$ , the argument of $\dfrac{z_1}{z_2}$ in degrees is$0$$30$$60$$90$

If $z$ is a complex variable, the value of $\displaystyle{} \int_{5}^{3i}\dfrac{dz}{z}$ is$− 0.511−1.57i$$− 0.511+1.57i$$0.511− 1.57i$$0.511+1.57i$

An analytic function of a complex variable $z = x + i y$ is expressed as $f (z) = u(x, y) + i v(x, y)$ , where $i=\sqrt{-1}$ . If $u(x, y) = x^2 − y^2$ , then expression...

An analytic function of a complex variable $z=x+iy$ is expressed as $f(z)=u(x,y)+iv(x,y)$ , where $i=\sqrt{-1}$ If $u(x,y)=2xy$, then $v(x,y)$ must be$x^2$+$y^2$+constant...

The argument of the complex number $\dfrac{1+\imath }{1-\imath }$ where $\imath =\sqrt{-1}$ ,isA. $-\pi$B. $\dfrac{-\pi }{2}$C. $\dfrac{\pi }{2}$ D. $\pi$