
Mark M. answered 04/25/22
Mathematics Teacher - NCLB Highly Qualified
z = 1 - i
||z|| = √2
θ = π / 4
z18 = (√2)18(cos (π/4)(18) + i sin (π/4)(18))
You to simplify and answer.

Madison P.
asked 04/25/22Mark M. answered 04/25/22
Mathematics Teacher - NCLB Highly Qualified
z = 1 - i
||z|| = √2
θ = π / 4
z18 = (√2)18(cos (π/4)(18) + i sin (π/4)(18))
You to simplify and answer.
(1-i)^18
=- 512i
=( sqr(1+1))^18)(cisx)^18
=2^9(cis18x)
=16(32)cis18x
= 512(cis18x)
= 512(cos18(7pi/4) + isin18(7pi/4)
= 512(cos63pi/2 + isin63pi/2)
=512(cos-pi/2 + isin-pi/2)
= 512(0 -i)
= -512i
check the answer
(1-i)^2 = 1-2i+1=-2i
(-2i)^2 = -4
(-4)^2 = 16
16^2 = 256
256(1-i)^2 =256(-2i)=-512i
which is actually much easier to do than DeMoivre's Theorem
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Robert K.
Mark, shouldn't 1 - i be Sqrt2Cis(7pi/4) rather than Sqrt2Cis(pi/4)? Checking algebraically, I get (1 - i)^18 = [(1- i)^2]^9 = [-2i]^9 = -512i04/25/22