Recently I calculated the Vm and the Vc. However I think the value is ackward and strange.
wrong --> Looks like your frequency varies from 3KHz to about 1.5KHertz.
Variation is 3 cycles per division, to 1.5 cycles per division, at 500uSec per division, thus 6KHz to 3KHz.
wrong -->The deltaF is 1,500 Hertz, suggesting 15 volts is the modulation input.
The correct deltaF is 3,000Hz, which at 100 Hertz/volt suggests 30 volts is the peak-peak modulation input.