My Math Forum trigonometic sine wave equation, Help guys please !

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 May 23rd, 2009, 02:12 PM #1 Newbie   Joined: May 2009 Posts: 1 Thanks: 0 trigonometic sine wave equation, Help guys please ! Hi guys, I got a math assignment due on Tuesday and am really stuck with no on to help me around. v1 = 20sin(theta -30) v2 = 30sin(theta +45) vr = v1 + v2 question 1) 1)plot v1,v2 and vr in the same graph 2)resultant equation should be written in the form of vr=Asin (theta + betha) 3) express 20sin ( theta-30) + 30sin (theta +45) in the form of Rsin (theta + alpha) this is the question , i can graph v1 and v2, but for vr , should i just put in values and add them ? and for 2 and 3 i don't how can i do the conversion ? any help is appreciated , thanks .
 May 23rd, 2009, 03:20 PM #2 Global Moderator   Joined: May 2007 Posts: 6,807 Thanks: 717 Re: trigonometic sine wave equation, Help guys please ! Short tutorial: I'll use capitals for known and x for unknown. You have terms of the form Asin(x+B) sine law gives you AcosBsinx+AsinBcox, where sinB and cosB are known. Add terms to get vr and you will have Msinx+Ncosx, where M and N are known. Now let L=(M^2+N^2)^1/2. So (M/L)^2 + (N/L)^2 = 1. Therefore M/L and N/L are cos and sin of a known angle C. vr=Lsin(x+C).

 Tags equation, guys, sine, trigonometic, wave

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