Can someone help me to find the mathematical expression that tells me in which section a point P is in?

first define the two straight lines: r & s

then find it’s analytic expression:

r : x → y & s : x → y

now we define sets:

{1} = {r(x) > 0} ⋃ {s(x) > 0}

{2} = {r(x) > 0} ⋃ {s(x) < 0}

…

you wold also need to define {r}, {s} & {r} ⋂ {s}.

Now a point can only be in one of the above sets and it will depend on r, s.