In the figure, two identical circles, with centres at A and B respectively, have an area of 0.785 cm each.
If A is directly above D, find the area of the shaded
region.

Yes, two vertical lines can be complementary

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.

Do you mean conversion factor?