Can any body help with this one. Evaluate the following using De Moivres Theorm's. (2+i)^3
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Originally Posted by heatly Can any body help with this one. Evaluate the following using De Moivres Theorm's. (2+i)^3 Start by converting $\displaystyle 2 + i$ to Polar form...
I did that and got, |2+i| = sqrt 5 z=(sqrt(5))^3 (cos pi/2 + i sin pi/2) ...... Which gives...0+11.18i ??? The ans is z= 2 + 11i
Last edited by heatly; Jul 29th 2010 at 02:51 AM.
I don't think you computed the angle correctly. Try $\displaystyle \theta=\tan^{-1}(\text{Im}(z)/\text{Re}(z)).$
thankyou very much you are correct Ackbeet.
You're welcome. Have a good one!
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