GATE ME 2014 Set 3 | Complex Variable Question 14 | Engineering Mathematics

GATE ME 2014 Set 3

MCQ (Single Correct Answer)

-0.6

An analytic function of a complex variable $$z = x + iy$$ is expressed as
$$f\left( z \right) = u\left( {x + y} \right) + iv\left( {x,y} \right),$$ where $$i = \sqrt { - 1} .$$ If $$u(x, y)=$$ $${x^3} - {y^2}$$
then expression for $$v(x,y)$$ in terms of $$x,y$$ and a general constant $$c$$ would be

$$xy+c$$

$${{{x^2} + {y^2}} \over 2} + c$$

$$2xy+c$$

$${{{{\left( {x - y} \right)}^2}} \over 2} + c$$

GATE ME 2007

MCQ (Single Correct Answer)

-0.6

If $$\phi (x,y)$$ and $$\psi (x,y)$$ are function with continuous 2^nd derivatives then $$\phi (x,y)\, + \,i\psi (x,y)$$ can be expressed as an analytic function of x +iy ($$i = \sqrt { - 1} $$) when

$${{\partial \phi } \over {\partial x}} = - {{\partial \psi } \over {\partial x}},\,{{\partial \phi } \over {\partial y}} = {{\partial \psi } \over {\partial y}}$$

$${{\partial \phi } \over {\partial y}} = - {{\partial \psi } \over {\partial x}},\,{{\partial \phi } \over {\partial x}} = {{\partial \psi } \over {\partial y}}$$

$${{{\partial ^2}\phi } \over {\partial {x^2}}} + {{{\partial ^2}\phi } \over {\partial {y^2}}} = {{{\partial ^2}\psi } \over {\partial {x^2}}} + {{{\partial ^2}\psi } \over {\partial {y^2}}} = 1$$

$${{\partial \phi } \over {\partial x}} + {{\partial \phi } \over {\partial y}} = {{\partial \psi } \over {\partial x}} + {{\partial \psi } \over {\partial y}} = 0$$