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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Specialist Mathematics => Topic started by: chickenpop on October 28, 2010, 05:10:11 pm

Title: Convert (-2)+ 2√3 i to polar form?
Post by: chickenpop on October 28, 2010, 05:10:11 pm: I keep on getting this wrong for some reason, think I'm missing something crucial

I always get (-pi/3) as the angle, but it's actually 2pi/3. What am I doing wrong? :-\
Title: Re: Convert (-2)+ 2√3 i to polar form?
Post by: 98.40_for_sure on October 28, 2010, 05:12:45 pm: Designate a reference angle and solve. Then according to quadrant, specify the actual angle
Title: Re: Convert (-2)+ 2√3 i to polar form?
Post by: InitialDRulz on October 28, 2010, 05:13:17 pm: well the negative 2 means its gonna be in the left hand side...

So yeah LOL
Title: Re: Convert (-2)+ 2√3 i to polar form?
Post by: superflya on October 28, 2010, 05:13:50 pm: graph it and see where the point lies, u subtract pi/3 from pi.
Title: Re: Convert (-2)+ 2√3 i to polar form?
Post by: vea on October 28, 2010, 05:14:06 pm: If you picture it, the point is in the 2nd quadrant (-2,2root3)

so tan(angle)=2root3/-2

=-root3

so angle=2pi/3 (because tan is negative in the 2nd quadrant)
Title: Re: Convert (-2)+ 2√3 i to polar form?
Post by: jasoN- on October 28, 2010, 05:14:47 pm: $-2 + 2\sqrt{3}i$ is in quadrant 2
ie. $Arg(z) = \pi -\theta$
$Arg(z) = \pi - tan^{-1} \frac{2\sqrt{3}}{2}$
$= \pi - \frac{\pi}{3}$
$= \frac{2\pi}{3}$
Title: Re: Convert (-2)+ 2√3 i to polar form?
Post by: Yitzi_K on October 28, 2010, 05:15:39 pm: Since Re(z) is negative, and Im(z) is positive, the angle must be in the second quadrant, hence it's 2pi/3.
Title: Re: Convert (-2)+ 2√3 i to polar form?
Post by: chickenpop on October 28, 2010, 05:48:25 pm: Oh, I feel so silly lol :P Thanks everyone