I typed a number divided by 0 on Wolfram Alpha and thought that it would say "undefined". However, when I pressed enter it told me that the answer is complex infinity.
I have always been taught that it is undefined and do not understand what complex infinity is. Is complex infinity just another way of saying undefined or does it mean something else?
Help would be appreciated.
Best Answer
Whether or not things are "undefined" largely depeneds on what framework you are working in.
If we are working in the naturals, we might say that $3-5$ is undefined.
There are many systems where it makes sense to assign $\frac{n}{0}$ some value. In this particular example, it is defined to be complex infinity, which can be thought of as follows: suppose we are looking at the complex plane. Similarly to how the complex number "0" is represented by a zero vector of arbitrary direction, we wish to associate all complex numbers of infinite absolute value (regardless of direction) to a single point.
This is complex infinity, and geometrically, by associating all complex numbers of infinite absolute value to be the same on the plane, we have formed a sphere, one with zero on the bottom, and complex infinity on the top. This is called the Riemann Sphere.