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QUICK asap math

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Let $R$ be the set of primitive $42^{\text{nd}}$ roots of unity, and let $S$ be the set of primitive $70^{\text{th}}$ roots of unity. How many elements do $R$ and $S$ have in common?

Jan 17, 2019

#1
+5664
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$$GCF(42,70)=7\\ \text{Thus the common roots of unity are}\\ \Large e^{\pm i 2\pi \frac{k}{7}},~\normalsize k=0,1,\dots ,6$$

$$\text{There are 14 of these}$$

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Jan 17, 2019

#1
+5664
+2
$$GCF(42,70)=7\\ \text{Thus the common roots of unity are}\\ \Large e^{\pm i 2\pi \frac{k}{7}},~\normalsize k=0,1,\dots ,6$$
$$\text{There are 14 of these}$$