We all know someone who acts tough online but soft irl

2-digit numbers less than 91 which are 1 less than a multiple of 10

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?

Is it true or false i’m trying to pass this test so i can leave school