Vertical angles are congruent according to the vertical angles theorem. If they are complementary as well, then they both sum up to 90 degrees. So, form an algebraic equation!
x+x=90 or 2x=90... Using the division property of equality, the angle measure (or x) equals 45...
Happy Solving!
The domain is the set of all possible x-values which will make the function "work", and will output real y-values

there is not a value for x, that makes the function does not "work", so x can take any value, in other words all real numbers
so, the answer is all real numbers
I don’t understand what you are asking?