Wednesday, January 12, 2011

Exponential Functions, Logarithmic Functions and Their Graphs

Definition of Logarithmic Functions:


         - eq=y=log_ax      can also be written as  eq=x=a^y...... they are equivalent.

The logarithmic function is called log base a


ex.   eq=log_327=x ........ which is the same as........ eq=3^x=27

       Then solve for x....... which is 3

Properties of Logarithms:


1. eq=log_a1=0    because    eq=a^0=1

2. eq=log_aa=1     because    eq=a^1=a

3. eq=log_ax =log_ay , then x = y  ----------- One-to-One property

Transformations of Graphs of Logarithmic Functions:


The graphs of logarithms are the same as the graphs for exponents but they are reflected over the line of y = x.
The transformations for logarithmic graphs are the same as transformations for any other kinds of graphs.


The best way to show this is in an example.


Ex.  eq=f(x)=log_e(x-1)+2
    - The transformations for this graph are the same as for any other graph
            - Moved to the right 1, and moved up 2.

Natural Logarithms:


The function is defined as:

        eq=f(x)=log_ex=ln x ,   x > 0     This is called the natural logarithmic function.


Properties of Natural Logarithms:


1. eq=ln1=0  
     because   eq=e^0=1
2. eq=lne=1     because    eq=e^1=e
3. eq=lnx=lny, the x=y  ------ One-to-One Property

James Thomas

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