Question

Test whether the following functions are analytic exp(x).(cos y + i sin y)

Answer 1

Answer:

The given f(z) is analytic function

i)  δU/δx   = eˣ (cos y) = δV/δy    

ii)  δU/δy   = eˣ (-sin y) = -  δV/δx  

Hence the CR - equations are satisfied

Step-by-step explanation:

Explanation:-

Analytic function:-

A point at which an analytic function ceases to posses a derivative is

called a singular point of the function.Thus the necessary and sufficient condition for a complex function f(Z) = U+i V is analytic in a region R are

δU/δx = δV/δy     and δU/δy = -δV/δx    ( C R equations)

Given f(Z) = eˣ(cos y+ i sin y)

Let          U = eˣ(cos y)   ....(i)

and

              V = eˣ(sin y) ....(ii)

Differentiating equation(i) partially with respective to 'x'

             δU/δx   = eˣ (cos y)

Differentiating partially equation(i) with respective to 'y'

             δU/δy    = eˣ (-sin y)

Differentiating equation(ii) partially with respective to 'x'

             δV/δx    = eˣ (sin y)

Differentiating equation(ii) partially with respective to 'y'

             δV/δy    = eˣ (cos y)

Now

          δU/δx   = eˣ (cos y) = δV/δy    

i)            δU/δx = δV/δy  

           δU/δy   = eˣ (-sin y) = -  δV/δx    

ii)         δU/δy = -  δV/δx    

Hence the CR - equations are satisfied

There fore the given f(z) is analytic function