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Find the square roots of a = root3 + root3*i

  • #1
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Member warned about not using the homework template
I don't recall ever doing this but maybe I have.

z2 = a = p [cos Ψ + i sin Ψ] = √3 + i*√3

p = √6
Ψ = π/4

Using the formula in the notes, z = 61/4 * exp[i*(π/4 + 2π*k)/2], k = 0, 1.
 
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Answers and Replies

  • #2
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I don't recall ever doing this but maybe I have.

z2 = a = p [cos(psi) + i sin(psi)] = root3 + i*root3

p = root6
psi = pi/4

Using the formula in the notes, z = 61/4 * exp[i*(pi/4 + 2pi*k)/2], k = 0, 1.
Do you have a question?

Also, your problem would be much more readable if you used LaTeX or the symbols available from the Advanced Menu, under the ##\Sigma## icon; e.g., √, ψ, and π.
 
  • #3
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When I multiply it out, I get -a.
 
  • #4
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When I multiply it out, I get -a.
I don't. What do you get for the two roots of ##\sqrt{6}(cos(\pi/4) + i sin(\pi/4))##?

Note that in polar form, what you're calling a is (##\sqrt{6}, \pi/4##).
 
  • #5
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I don't. What do you get for the two roots of ##\sqrt{6}(cos(\pi/4) + i sin(\pi/4))##?

Note that in polar form, what you're calling a is (##\sqrt{6}, \pi/4##).
That's odd. I used my TI-89 to check my work, and it gave me -a. Maybe I had a typo.
 
  • #6
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That's odd. I used my TI-89 to check my work, and it gave me -a. Maybe I had a typo.
Possibly, or maybe it's in degree mode when it should be in radian mode.

Either way, this is an easy enough problem that a calculator shouldn't be needed. ##cos(\pi/4) = sin(\pi/4) = \frac{\sqrt{2}}{2} \approx .707##

Again, what did you get for the two roots?
 
  • #7
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Possibly, or maybe it's in degree mode when it should be in radian mode.

Either way, this is an easy enough problem that a calculator shouldn't be needed. ##cos(\pi/4) = sin(\pi/4) = \frac{\sqrt{2}}{2} \approx .707##

Again, what did you get for the two roots?
From the original post, z2 = {61/4*ei*9π/8, 61/4*ei*π/8}
 
  • #8
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From the original post, z2 = {61/4*ei*9π/8, 61/4*ei*π/8}
There's your mistake. Those are the correct roots of the equation z2 = ##\sqrt{6}(cos (\pi/4) + i sin (\pi/4))##, but they are values of z, not z2.

If you square each of them, you get ##\sqrt{6}(cos (\pi/4) + i sin (\pi/4))##.
 
  • #9
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There's your mistake. Those are the correct roots of the equation z2 = ##\sqrt{6}(cos (\pi/4) + i sin (\pi/4))##, but they are values of z, not z2.

If you square each of them, you get ##\sqrt{6}(cos (\pi/4) + i sin (\pi/4))##.
Ah. For some reason I thought that those were the square roots, not that each of those was a square root. Thanks for the help. My brain is still on vacation. Haha.
 

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