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Logarithmic identities

Edited by So8res last updated 28th May 2016

Recall that logb(n) is defined to be the (possibly fractional) number of times that you have to multiply 1 by b to get n. Logarithm functions satisfy the following properties, for any base b:

  • Inversion of exponentials: blogb(n)=logb(bn)=n.
  • Log of 1 is 0: logb(1)=0
  • Log of the base is 1: logb(b)=1
  • Multiplication is addition in logspace: logb(x⋅y)=logb(x)+logb(y).
  • Exponentiation is multiplication in logspace: logb(xn)=nlogb(x).
  • Symmetry across log exponents: xlogb(y)=ylogb(x).
  • Change of base: loga(n)=logb(n)logb(a)
Parents:
Logarithm
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