1. Sullivan Algebra and Trigonometry: Section 6.1
Objectives of this Section
Determine the Inverse of a Function
Obtain the Graph of the Inverse Function From the Graph of the Function
Find the Inverse Function f -1

2. one-to-one not one-to-one
A function f is said to be one-to-one if, for any choice of numbers x1 and x2, x x2, in the domain of f, then f (x1) f (x2).
Which of the following are one - to - one functions?
{(1, 1), (2, 4), (3, 9), (4, 16)}
one-to-one
{(-2, 4), (-1, 1), (0, 0), (1, 1)}
not one-to-one

3. Theorem Horizontal Line Test
If horizontal lines intersect the graph of a function f in at most one point, then f is one-to-one.
Use the graph to determine whether the following function is one - to - one. x y
(0,0)

4. Use the graph to determine whether the following function is one - to - one.x y
(1,1)
(-1,-1)

5. Let f denote a one-to-one function y = f (x)
Let f denote a one-to-one function y = f (x). The inverse of f, denoted f -1, is a function such that f -1(f (x)) = x for every x in the domain f and f (f -1(x)) = x for every x in the domain of f -1.
In other words, the function f maps each x in its domain to a unique y in its range. The inverse function f -1 maps each y in the range back to the x in the domain.

6. Domain of f
Range of f

7. The graph of a function f and the graph of its inverse are symmetric with respect to the line y=x.

8. Finding the inverse of a function.
Since the domain of f is the range of f -1 and visa versa, we find the inverse of f by interchanging x and y. f x ( ) , = - π 5 3
Example: Find the inverse of

9. To determine if two given functions are inverses, we use the definition of inverse functions. If two functions are inverses, then f -1(f (x)) = x and f (f -1(x)) = x.