Which type of chevrons is applied on the B787? Which type of chevron nozzle was applied on the B787? I'm really confused about whether if it's sawtooth or sine wave.
Strictly speaking, its neither. Chevrons don't resemble either a sawtooth wave or a sine wave in mathematical terms. The closest is that it is a smoothed (modified) saw tooth form.

Image from compositesworld.com
Though the initial research used a serrated nozzle in saw tooth form, the final commercial application differs from it. However, the chevrons are repeatedly noted as having a saw tooth form, by NASA among others:

One of the most recent noise-reducing technologies shepherded through the research process by NASA and now making a difference on commercial jet engines is chevrons.
Chevrons are the sawtooth pattern seen on the trailing edges of some jet engine nozzles.

So, it's a choice between saw tooth and sine wave, its better to go with the former.
GE's patent for the Chevron describes the shape as triangular with qualifications:

... each of said chevrons being triangular in configuration
... said chevrons having a compound concave contour both axially between said bases and apexes and laterally between said trailing edges..


Image from Chevron exhaust nozzle for a gas turbine engine