1. Lesson 64
Using logarithms

2. logarithm
A logarithm is the exponent that is applied to a specific base to obtain a given value.
Every exponential equation has a logarithmic form and vice versa.
Exponential form logarithmic form
bx = a logb a = x
"log base b of a equals x"

3. Converting from exponential to logarithmic form
Write each exponential equation in logarithmic form.
25 = log2 32 = 5
exponent
base

4. practice Write in logarithmic form. 51 = 5 80 = 1 35 = 243 4-2 = .0625
82 = 64
63 = 216

5. Converting from logarithmic form to exponential form
Write the logarithmic equation in exponential form.
Log =3
Look for exponent and base
3 is the exponent and 10 is the base
103 = 1000

6. practice Write in exponential form. Log7 7 = 1 Log3 81 = x

7. Common logarithm A logarithm with base 10 is called a common logarithm
If no base is written, the base is assumed to be 10
Example:
log 5 is the same as log10 5

8. Lab 10
Using the log keys

9. Calculate 4 log (5) Calculate 4log (5) Press 4 log 5 ) Press ENTER
To calculate the natural logarithm
Calculate 4 ln(5)
Press 4 ln 5)