Mathematics
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OpenStudy (dschneider2016):
Please help!!! Find Medal!!!
Find the cube roots of 8(cos 216° + i sin 216°)
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OpenStudy (dschneider2016):
@jdoe0001 @whpalmer4
OpenStudy (dschneider2016):
@satellite73
OpenStudy (anonymous):
what is the cubed root of 8?
OpenStudy (dschneider2016):
2
OpenStudy (anonymous):
good,
what is \(216\div3\)?
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OpenStudy (dschneider2016):
72
OpenStudy (anonymous):
then one answer is \[2\left(\cos(72^\circ)+i\sin(72^\circ)\right)\]
easy right?
OpenStudy (dschneider2016):
yes! how do I find the other ones?
OpenStudy (anonymous):
ready to find the other ones?
OpenStudy (anonymous):
what is
\(216+360\)? (we are going around the circle again)
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OpenStudy (dschneider2016):
576
OpenStudy (anonymous):
ok i believe you
what is \(576\div3\)?
OpenStudy (dschneider2016):
192
OpenStudy (anonymous):
ok so answer 2 is \[2\left(\cos(192^\circ)+i\sin(192^\circ)\right)\]
OpenStudy (anonymous):
lather, rinse, repeat
you only have to do it one more time
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OpenStudy (dschneider2016):
great! So would I add 720 to 216 and then divide by 3 to find the next one
OpenStudy (anonymous):
yes
OpenStudy (dschneider2016):
2(cos(312∘)+isin(312∘))
OpenStudy (anonymous):
same as dividing the unit circle in to three parts, with 72 as one of them, but it is just as easy to keep adding 360
OpenStudy (anonymous):
yes
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OpenStudy (anonymous):
see how easy that is?
OpenStudy (dschneider2016):
Great! SO is that all?
OpenStudy (dschneider2016):
Thank you so much!!
OpenStudy (anonymous):
yes
that is pretty much the whole point of writing \(a+bi\) in trig form
otherwise this would be very very hard
OpenStudy (anonymous):
yw