Calculate Euler's phi function (also called totient function) Φ(90)\Phi(90)Φ(90).
參考答案與解析
Φ(90)=24\Phi(90)=24Φ(90)=24。90=2×32×590=2\times3^2\times590=2×32×5，Φ(90)=90×(1−12)(1−13)(1−15)=90×12×23×45=24\Phi(90)=90\times(1-\frac12)(1-\frac13)(1-\frac15)=90\times\frac12\times\frac23\times\frac45=24Φ(90)=90×(1−21)(1−31)(1−51)=90×21×32×54=24。
