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Let z=2+32+i232

 

Find 1+z+z2+z3++z2016

 May 22, 2020
 #1
avatar+33657 
+3

The sum is 1.  See the following:

 

 May 22, 2020
 #2
avatar+26397 
+2

Let
z=2+32+i232
Find

1+z+z2+z3++z2016

 

z=2+32+i232z=(2+32)2+(232)2eiarctan(232+3)z=1eiπ12z=eiπ12

 

Sum of a geometric sequence

1+z+z2+z3++z2016=z20171z1=(eiπ12)20171eiπ121=ei201712π1eiπ121=ei302551ei151=cos(30255)+isin(30255)1cos(15)+isin(15)1=cos(15)+isin(15)1cos(15)+isin(15)11+z+z2+z3++z2016=1

 

laugh

 May 22, 2020

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