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Projectile Motion Proof/Hassle 
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#1
Oct2306, 07:22 PM

P: 7

This is a real pain and I'm getting nowhere. If you can't see the image look at the attached file.
Angle a(upper angle)=Theta Angle b(lower angle)=Beta Prove these relations: a) Rsin2theta+d(1+cos2theta)=(R^2)/Rnot where Rnot= ((vnot)^2)/g b) That Rm(meaning maximum R) happens for tan2(thetamax)=Rm/d c) 2thetamax+alpha=90 degrees d) (Rnot^2)+2dRnot=Rm^2 For a) I'm getting down to 2costheta(Rsintheta+dcostheta)=(R^2)/Rnot But I don't see the next step, maybe I went too far. Or do I need to include Beta somewhere? I don't think I do. There is some trig relation or relating it to the diagram that I just don't see. All I really need is help on a)then I can use what I know from a) to solve for b) and each one after can be done likewise however I won't get to them if I can't get a) done. Please HELP! 


#2
Oct2306, 10:49 PM

Sci Advisor
HW Helper
P: 3,031

2costheta(Rsintheta+dcostheta)=(R^2)/Rnot
R(sinthetacostheta+costhetasintheta)+2dcos^2theta)=(R^2)/Rnot Do you remember any trig identities? http://www.sosmath.com/trig/Trig5/trig5/trig5.html 


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