Which basic operations are undefined even for complex numbers?

Question

I'm aware of:

• $\frac{X}{0}$ (dividing by zero)
• $0^0$ (raising zero to the power of zero)

Are there any others?

Answer 1

There's always $\infty-\infty$ which tends to go wrong, since you do not know which is the "larger" infinity.

Or you could consider $\infty \times i$ and $\infty i- \infty i$. (keeping it complex)