Day 4 ­ Change of Base formula and calculator .notebook
November 19, 2014
Unit F (part 2) Logarithmic functions and their properties (A.4.A.)
Objective: To convert expressions from exponential form to logarithmic form (and
back again)
To solve logarithmic equations using rules of exponents.
To use the calculator to solve log base 10 and base e
Too use the Change of Base Formula to evaluate expressions
Do have
you these
memorized yet?
1) logb1=0
2) logbb=1
3) logbbx=x
There are 2 special logarithms:
4) logbxr = rlogbx
Common log: y=log10x or y=log x
Natural log: y=logex or y=ln x
5) logbrs=logbr + logbs
6) logb = logbr - logbs
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Day 4 ­ Change of Base formula and calculator .notebook
log
November 19, 2014
=
What are the restrictions on ....
?
>0 and ?
>0
?
= 1
anything
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Day 4 ­ Change of Base formula and calculator .notebook
November 19, 2014
1) 3x=20
(Now solve by "logging" both sides and use your
Properties of logs....particularly base 10 and
base e)
2) 2-x = 10
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Day 4 ­ Change of Base formula and calculator .notebook
November 19, 2014
3) ex= 9
4) 2.2
(x-5)
= 9.32
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Day 4 ­ Change of Base formula and calculator .notebook
5) 12
(x-4)
November 19, 2014
(x-2)
=3
6) 2(x-1) = 1
8
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Day 4 ­ Change of Base formula and calculator .notebook
November 19, 2014
2x
7) 500 = 5e
8) x =log5 121
What do you do here? Hmmm...
Introducing...the Change of Base Formula
logca = log a or logca = ln a
ln c
log c
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Day 4 ­ Change of Base formula and calculator .notebook
November 19, 2014
9) x = log3 44.1
Homework: WS #4
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Day 4 ­ Change of Base formula and calculator .notebook
November 19, 2014
8