Scope mesurment two chanels

Hello.
Can u help me to understand if i want to measure to signals say one of them 100khz and the second is 1khz wich one of the should be the triger on scope.
Thx.

It depends on which waveform you wish to view without jitter.

Also on whether you want to examine where the two signals coincide, etc.

Going by first thought, you would trigger on the slower signal, and set the sweep time to view the entire waveform.