Question

What is the union of the 4 half-planes determined by 2 intersecting lines.
a. the entire plane
b. the entire plane except for the two intersecting lines
c. the entire plane except for one of the lines
d. the entire plane except for the point of intersection
e. None of the Above

Answer 1

Did you make a sketch of 2 intersection straight lines?
What is meant by "union" ?

Answer 2

All the elements in the set: union
Its pretty much asking what is contained in 4 half-planes