How to write a validation condition for a function?

Question

Java

I need a domain of definition, I am writing a program that displays the value of the start point x + step and calculates the value of the function to the end point, I need to write a condition when the error "function is undefined" will be displayed and when the value will be calculated by the formula.

I am writing in java (beginner, only scanner, loops, data types, formatted output)
For example, x initial = 1, x final = 10, step s = 1
There will be similar values ​​(taken from another function:
1.00 not defined
2.00 not defined
3.00 not defined
4.00 1.41
5.00 1.43
6.00 2.12
7.00 not defined
8.00 not defined
9.00 not defined
10.00 2.30

Answer 1

This function is not defined for x < 0 or 1-cos(x) = 0. I.e. If x < 0 or x= pi/2+2pi*k.
In the program, calculate the function in steps. First, the denominator, if it turned out to be 0 - not defined. Otherwise, see that the numerator can be calculated (x>=0).