Earth has a low air pressure zone at the Equator because . air is cold and sinks toward the surface of Earth there
air is warm and moves away from the surface of the Earth there
air is cold and moves away from the surface of the Earth there
air is warm and sinks toward the surface of the Earth there

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.