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In Problems 41–52, write each expression in the standard form a+bi.

49.(1-i)5

Short Answer

Expert verified

(1-i)5=-4+4i.

Step by step solution

01

Step 1. Rewrite 1-i in the form r(cos∅+isin∅).

The magnitude of 1-i is

12+(-1)2=1+1=2

which gives

(1-i)=2(12-12i)=2(cosπ4-isinπ4)

02

Step 2. Using De Moivre's Theorem.

We know that if a complex number is z=r(cos∅+isin∅)then zn=rn[cos(n∅)+isin(n∅)].

This gives

role="math" localid="1646763868779" (1-i)5=[2(cosπ4-isinπ4)]5=[(2)5(cos{5×π4}-isin{5×π4})]=42(cos5π4-isin5π4)=42(-12-i(-12))=-4+4i

So,(1-i)5=-4+4i

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