The 'trigger' settings determine when the trace begins. suppose you have displayed a sine wave at v = vosin(wt) on the screen, where vo = 3v and w/2t = 5khz. assume further that the signal triggers the scope when v = 1.5v and wt = 30 degrees.
suppose you double th amplitude of the wave without changing any oscilloscope settings. when are v and wt now when the scope is triggered? [ the level hasn't changed so th scope still triggers when v = 1.5v. v = 1.5 = 6sin(wt); wt=sin^-1(1.5/6) = 14.477512851511 degrees]

assume that you reduce vo back to 3v ans switch the trigger slope polarity from '+' to '-' without changing the trigger level dial. what are the v and wt when the scope is triggered now?