# Help with graphical technique of adding 2 sinusoids

#### p75213

Joined May 24, 2011
70
I have a problem understanding how equation 9.11 (see attached) works with Fig. 9.4 (a). Can somebody please clarify?

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#### jegues

Joined Sep 13, 2010
733
I have a problem understanding how equation 9.11 (see attached) works with Fig. 9.4 (a). Can somebody please clarify?
Put both of the sinusoids into the phasor domain, add them, and pull them back to the time domain.

Use the cosine as your reference phasor.

#### Rio

Joined Dec 23, 2010
22
u can prove that mathematically by ,, let's say A=4 , B=3
and then assume that wt = 0 and replace it in the equation (Acoswt+Bsinwt) and write down the number you have and then when wt=-1 , and then wt = 1 and when u have it ready draw it ,, and u will have a cosine function with a small shift

#### t_n_k

Joined Mar 6, 2009
5,455
Hi p75213 - It's not particularly clear where the gap in your understanding lies. Perhaps you are not sure why one is permitted to draw the cosine and sine function vectors (phasors) as an orthogonal pair - i.e. at right angles to one another ...?? Do you understand why/how it's possible to represent a time varying function as a 'static' phasor?