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1
Objectives
c
Understand the uses for logarithms and
apply them to earthquake and pH
problems
c
Write expressions in logarithmic form
c
Evaluate logarithms
c
Graph logarithmic functions (we’ll probably
leave this until tomorrow)
Why do we study logarithms?
http://opinionator.blogs.nytimes.com/2010/03/28/powertools/#more43171
c
If you think of functions as tools, we need tools
that can undo each other, like a stapler and a
staple remover
r
Ex: quadratic and square root function
c
Logarithms are the inverses of exponential
functions.
c
They are also compressors and can be used to
make huge numbers more manageable. (The
difference between 100 and 100million)
The Richter Scale
c
The Richter Scale is the perfect example
of logarithms at work
c
Moving one unit to the right on the Richter
Scale releases about 30 times as much
energy
Comparing seismic energy
c
The earthquake in Haiti this year
registered a 7.0 on the Richter Scale. In
1960, an earthquake of 9.5 shook Chile.
Compare the amounts of energy released
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 Fall '09
 Johnson
 Algebra, Logarithmic Functions

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