The expression that is not an indeterminate form is 1^∞.

Here's a breakdown of each option:

1. 0^0: Indeterminate, as it can be argued to be either 0 or 1 depending on the context.
2. ∞^0: Indeterminate, because it depends on how the limits approach infinity.
3. 0^∞: Indeterminate, since it can lead to different results depending on the function approaching 0 and ∞.
4. 1^∞: This evaluates to 1, so it is not indeterminate.

Would you like further explanations on any of these concepts? Here are some related questions:

1. Why is $0^0$ considered indeterminate in some contexts?
2. How does the concept of limits apply to $∞^0$?
3. Can you provide examples where $0^∞$ is used in calculus?
4. In what scenarios might $1^∞$ be encountered?
5. What are other common indeterminate forms in calculus?

Tip: Always consider the context of limits when determining if an expression is indeterminate.