8^x=1 Please solve for x.

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

Ineed me i stuck and i don’t want to get it wrong

Write a function for a rotation 90 degrees counter clockwise about the origin, point 0