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Q- Let m and n be coprime. Show that\phi(mn) = \phi(m) * \phi(n). Hint: when does a pair of residues modulo m and n have an inverse.
The Euler Totient Function for coprime numbers states that if m and n are coprime, then the relationship \(\phi(mn) = \phi(m) \times \phi(n)\) holds true. This is derived from the structure of the multiplicative group of integers modulo mn, represented as \((\mathbf{Z}/mn\mathbf{Z})^{\times} = (\mathbf{Z}/m\mathbf{Z})^{\times} \times (\mathbf{Z}/n\mathbf{Z})^{\times}\). The proof involves analyzing the orders of both sides of the equation, confirming that the totient function behaves multiplicatively for coprime integers.
PREREQUISITESMathematicians, students of number theory, and anyone interested in the properties of coprime integers and the Euler Totient Function.