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# I don't understand...

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For a positive integer $$n$$$$\phi(n)$$denotes the number of positive integers less than or equal to $$n$$ that are relatively prime to $$n$$.  What is $$\phi(2^{100})$$?

Guest Oct 14, 2018

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$$\text{The odd numbers will be relatively prime to }2^{100} \\ \text{so }\phi(2^{100}) = \dfrac 1 2 2^{100} = 2^{99}$$

Rom  Oct 14, 2018
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$$\text{The odd numbers will be relatively prime to }2^{100} \\ \text{so }\phi(2^{100}) = \dfrac 1 2 2^{100} = 2^{99}$$