Wednesday, September 28, 2011

Chapter 1.5 - Inverse Functions

The inverse of a function is when all of the x and y coordinates are switched.

Example: The inverse of (1,2) (2,4) (3,6) is (2,1) (4,2) (6,3)

To find the inverse of a function you must switch the x and y variable and then solve for y. This is denoted by . The domain of must be equal to the range of , and the range of must be equal to the domain of .

Example: If then

To verify that you found the inverse of the function you can compose one to the other and it should equal x. If it doesn't then you did something wrong.

Example:

The graph of a function and its inverse are reflected across the line .

Example: The red graph is and the green graph is .



Not all functions have inverses that are functions.

Example:
The red graph is
The green graph is the inverse which is
The inverse if the red graph (green graph) is not a function because it doesn't pass the vertical line test.


Monday, September 26, 2011

Chapter 1.4 - Combinations of Functions

Arithmetic Combinations of Functions

Just like two real numbers, functions can be combined by the operations of addition, subtraction, multiplication, and division.

Definitions:

The domain of an arithmetic combination of functions f and g consists of all real numbers that are common to the domains of f and g.

Examples:

If and , find the sum, difference, product, and quotient of f and g.

Sum:
Difference:
Product:
Quotient:

Compositions of Functions

Another way of combining two functions is to form the composition of one with the other.

Definition:
The composition of the function f with g is .

The domain of is the set of all x in the domain of g such that g(x) is in the domain of f.

Example:

Find for and . If possible, find and .


The domain of is [1, ∞). So = is defined, but is not defined because 0 is not in the domain of .

Tuesday, September 20, 2011

Even and Odd Functions

Even function: symmetric to the y axis
Example:
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Odd Function: symmetric to the origin

Example:

Note: In an odd function the line that connects the two points passes through the origin


There can also be functions that are neither even or odd