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Precalculus 9 Online
OpenStudy (anonymous):

Find the fifth roots of 243(cos 240° + i sin 240°).

OpenStudy (amistre64):

^5 the outside and *5 the innards

OpenStudy (amistre64):

err, thats 1/5, not 5

OpenStudy (anonymous):

its still confusing to me

OpenStudy (amistre64):

[ k (cos a + i sin a) ]^n k^n (cos na + i sin na)

OpenStudy (amistre64):

243(cos 240° + i sin 240°) ^(1/5) , for 5th roots 243^(1/5) (cos 240°/5 + i sin 240°/5)

OpenStudy (amistre64):

might have to cycle thru 1/5 2/5 3/5 4/5 5/5 to determine all the 5th roots

OpenStudy (amistre64):

there seems to be an exponential form as well, but thats just confusing me to read :/

OpenStudy (anonymous):

i get that the first is (cos50+isin50)

OpenStudy (amistre64):

essentially, you are dividing a circle into 5 equal portions: 360/5 = 72 and then rotating your starting angle by 72 to get 5 complex values all together

OpenStudy (amistre64):

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