I was wondering how to make such lines in Sketch:
I found an interesting solution elsewhere on the internet: use the grid tool.
Draw the first 3 points using the
vector tool (V) and then Arrange > Make Grid....
There you define 1 row and how many repetitions you want as columns, with Margin 0px. After that you better use Layer > Path > Join to make it a single object.
For the sinusoidal lines you just convert the points from
Mirrored and delete the first and last point, as this will deform them. Play around with horizontal or vertical scale if you want to make the shapes tighter.