对数的换底公式
log(a) b=log(m) b / log(m) a
括号里的是底数
推导：设log(m) b=P,log(m) a =Q,log(a) b=R
则m^P=b,m^Q=a,a^R=b
即(m^Q)^R=a^R=b
m^(QR)=b
所以P=QR,即R=P/Q,log(a) b=log(m) b / log(m) a
你的公式:
log(a) b * log(b) c * log (c) d
=log(m) b / log(m) a * log(m) c / log(m) b * log(m) d / log(m) c
=log(m) d / log(m) a
=log(a) d