8. point z is a(n) (hint: what type of lines are ox and nb? )
orthocenter
incenter
circumcenter
centroid

Point Z is an incenter because NB and OX are the bisectors of ∡N and ∡O.

20 percentage, you can also do it on a calculator.

Period is the time it takes for one “cycle” to complete. in the parent sine function, period is 2*pi since sin(0) = 0, sin(pi/2) = 1, sin(pi) = 0, sin(3pi/2) = -1, and sin(2pi) = 0. at that point, the sequence repeats itself. i’m not sure if your graph is similar to the sine function since you didn’t provide a picture, but you can find the period by looking at a graph.