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Question Number 8336 by Rasheed Soomro last updated on 08/Oct/16

Determine smallest n(≠0), for which  (ω+i)^n =1.

$$\mathrm{Determine}\:\mathrm{smallest}\:\mathrm{n}\left(\neq\mathrm{0}\right),\:\mathrm{for}\:\mathrm{which} \\ $$$$\left(\omega+\mathrm{i}\right)^{\mathrm{n}} =\mathrm{1}. \\ $$

Commented by prakash jain last updated on 08/Oct/16

w=cos ((2π)/3)+isin ((2π)/3)=−(1/2)+i((√3)/2)  w+i=−(1/2)+i(((√3)/2)+1)  ∣w+i∣=(√(((1/2))^2 +(((√3)/2)+1)^2 ))  =(√((1/4)+1+(3/(4+2(√3)))))=(√(2+(√3)))  Since ∣w+i∣=(√(2+(√3)))  of (w+i)^n =1⇒n=0  There is no value of n≠0 for which  (w+i)^n =1

$${w}=\mathrm{cos}\:\frac{\mathrm{2}\pi}{\mathrm{3}}+{i}\mathrm{sin}\:\frac{\mathrm{2}\pi}{\mathrm{3}}=−\frac{\mathrm{1}}{\mathrm{2}}+{i}\frac{\sqrt{\mathrm{3}}}{\mathrm{2}} \\ $$$${w}+{i}=−\frac{\mathrm{1}}{\mathrm{2}}+{i}\left(\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}+\mathrm{1}\right) \\ $$$$\mid{w}+{i}\mid=\sqrt{\left(\frac{\mathrm{1}}{\mathrm{2}}\right)^{\mathrm{2}} +\left(\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}+\mathrm{1}\right)^{\mathrm{2}} } \\ $$$$=\sqrt{\frac{\mathrm{1}}{\mathrm{4}}+\mathrm{1}+\frac{\mathrm{3}}{\mathrm{4}+\mathrm{2}\sqrt{\mathrm{3}}}}=\sqrt{\mathrm{2}+\sqrt{\mathrm{3}}} \\ $$$$\mathrm{Since}\:\mid{w}+{i}\mid=\sqrt{\mathrm{2}+\sqrt{\mathrm{3}}} \\ $$$$\mathrm{of}\:\left({w}+{i}\right)^{{n}} =\mathrm{1}\Rightarrow{n}=\mathrm{0} \\ $$$$\mathrm{There}\:\mathrm{is}\:\mathrm{no}\:\mathrm{value}\:\mathrm{of}\:{n}\neq\mathrm{0}\:\mathrm{for}\:\mathrm{which} \\ $$$$\left({w}+{i}\right)^{{n}} =\mathrm{1} \\ $$

Commented by Rasheed Soomro last updated on 09/Oct/16

Thanks a lot!

$$\mathrm{Thanks}\:\mathrm{a}\:\mathrm{lot}! \\ $$

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