Does the Limit in the Complex Plane Approach Infinity?

In summary, the limit as z approaches i of (z^2-1)/(z^2+1) is undefined, as it results in division by zero. Approaching from different directions gives different results, indicating that the limit does not exist. This is similar to the limit of 1/x, where approaching from different directions also gives different results, and the limit is undefined.
  • #1
cragar
2,552
3

Homework Statement


lim as z--> i , [itex] \frac{z^2-1}{z^2+1} [/itex]

The Attempt at a Solution


[/B]When we plug in i we get -2/0, so we get division by 0, Does this mean the limit is
infinity, I also tried approaching from z=x+i where x went to 0, you get the same answer,
I also approached from z=yi where y approaches 1, and I got the same answer.
 
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  • #2
cragar said:

Homework Statement


lim as z--> i , [itex] \frac{z^2-1}{z^2+1} [/itex]

The Attempt at a Solution


[/B]When we plug in i we get -2/0, so we get division by 0, Does this mean the limit is
infinity, I also tried approaching from z=x+i where x went to 0, you get the same answer,
I also approached from z=yi where y approaches 1, and I got the same answer.
What happens with ##\lim_{x \to 0} \frac 1 x##? Is the limit here ##\infty## or does the limit simply not exist at all? IOW, are the two one-sided limits equal?
 
  • #3
good point if we appraoch x from the left it goes to minus infinity , and if we approach from the right it is positive infinity, so the limit does not exist.
 

Related to Does the Limit in the Complex Plane Approach Infinity?

What is a limit in the complex plane?

A limit in the complex plane is a fundamental concept in calculus that describes the behavior of a function as the input approaches a certain point in the complex plane. It is defined as the value that the function approaches as the input gets closer and closer to the specified point.

How is a limit in the complex plane different from a limit in the real plane?

A limit in the complex plane is similar to a limit in the real plane, but it involves two-dimensional numbers known as complex numbers. These numbers have both a real and imaginary component, which allows for more complex behavior of functions compared to real numbers.

What are some common techniques for finding a limit in the complex plane?

Some common techniques for finding a limit in the complex plane include direct substitution, factoring and simplifying, using L'Hopital's rule, and using algebraic manipulations such as conjugates or rationalizing the denominator.

What is the importance of limits in the complex plane in mathematics and science?

Limits in the complex plane are crucial in mathematics and science as they help us understand and analyze the behavior of functions, which are essential in many fields such as physics, engineering, and economics. They also play a significant role in the development of advanced mathematical concepts and techniques.

Can a function have a limit in the complex plane but not in the real plane?

Yes, a function can have a limit in the complex plane but not in the real plane. This is because complex functions can exhibit more complex behavior, such as oscillations, that cannot be captured by real functions. In such cases, the limit in the real plane does not exist, but the limit in the complex plane may still exist and be well-defined.

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