Prove that tan squared a plus cot squared a equals 1 is not a trigonometric identity

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?

100 points, hi, i’m not sure how to get the equation from the graph and table.

Sum is 17 and their difference is 3