Chapter 6: Problem 45
Show that addition of complex numbers is associative, meaning that $$ u+(w+z)=(u+w)+z $$ for all complex numbers \(u, w,\) and \(z\).
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Chapter 6: Problem 45
Show that addition of complex numbers is associative, meaning that $$ u+(w+z)=(u+w)+z $$ for all complex numbers \(u, w,\) and \(z\).
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Write $$ \frac{1}{7\left(\cos \frac{\pi}{9}+i \sin \frac{\pi}{9}\right)} $$ in polar form.
In Example 6 , we found cube roots of 1 by finding numbers \(\theta\) such that $$ \cos (3 \theta)=1 \text { and } \sin (3 \theta)=0 $$ The three choices \(\theta=0, \theta=\frac{2 \pi}{3},\) and \(\theta=\frac{4 \pi}{3}\) gave us three distinct cube roots of 1 . Other choices of \(\theta\), such as \(\theta=2 \pi, \theta=\frac{8 \pi}{3},\) and \(\theta=\frac{10 \pi}{3},\) also satisfy the equations above. Explain why these choices of \(\theta\) do not give us additional cube roots of \(1 .\)
Suppose \(z\) is a nonzero complex number. Show that \(\bar{z}=\frac{1}{z}\) if and only if \(|z|=1\).
Show that addition of complex numbers is commutative, meaning that $$ w+z=z+w $$ for all complex numbers \(w\) and \(z\). [Hint: Show that $$ (a+b i)+(c+d i)=(c+d i)+(a+b i) $$
Write each expression in the form \(a+b i,\) where \(a\) and \(b\) are real numbers. $$ (1+\sqrt{3} i)^{3} $$
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