the 2 signals shown are used for modulating ( DSB-SC) a carrier with frequency fc.
Now i need to find the similarities and differences between their time domain representation.
Clearly the both will have same envelope. Now i tried for the difference part but could not find it. One possibility according to me can be the phase change at t=1. Can we find that what will be the phase change for both modulated signals at t =1 without drawing the actual plot ?

 

the 2 signals shown are used for modulating ( DSB-SC) a carrier with frequency fc.
Now i need to find the similarities and differences between their time domain representation.
Clearly the both will have same envelope. Now i tried for the difference part but could not find it. One possibility according to me can be the phase change at t=1. Can we find that what will be the phase change for both modulated signals at t =1 without drawing the actual plot ?

As far as the modulator is concerned,the fundamental frequency of waveform(b) is double that of waveform (a).

The modulator probably does not care if the negative 1/2 cycles of (b) go to zero volts rather than negative,all it sees is an increase in frequency, & a decrease in amplitude.

Yes the envelope shape will be the same.