Sketch Graphs: Struggling with Blue Highlighted Part

[gomes.]

Im meant to sketch these 2 graphs, but i can't seem to know what to do with the part highlighted in blue.

And I am think then I am meant to draw it for a few periods. But i can't continue because i don't know how to draw the part in blue?

 

[tiny-tim]

hi gomes!

for the left-hand graph, just draw a little "x" at the position (0, 1/2) …

it's understood that only the point at the centre of the "x" is actually meant!

(and then repeat for a few periods, as you say)

(oh, i think some people draw a dot with a circle round it instead)

 

[gomes.]

thanks! And how big should the circle be? If i where to do it that way?

 

[tiny-tim]

about the size you've done them …

but your circles are so wonky, i think you should go for the crosses … they're easier to draw!