1. 1.3 Exponential Functions
Acadia National Park, Maine
Greg Kelly, Hanford High School, Richland, Washington
Photo by Vickie Kelly, 2008

2. Although some of today’s lecture is from the book, some of it is not
Although some of today’s lecture is from the book, some of it is not. You must take notes to be successful in calculus.

3. We will be using the TI-89 calculator in this class.
You may use either the TI-89 Titanium or the older TI-89.
TI-89
The pictures in the lectures will usually illustrate the older TI-89.
Although the buttons on the Titanium Edition are different shapes and colors, they are in the same positions and have most of the same functions.
TI-89 Titanium

4. This is an example of an exponential function:
If $100 is invested for 4 years at 5.5% interest, compounded annually, the ending amount is:
On the TI-89:
ENTER
At the end of each year, interest is paid on the amount in the account and added back into the account, so the amount of increase gets larger each year.
This is an example of an exponential function:
exponent
base

7. Graph for in a [-5,5] by [-2,5] window:
MODE
Graph…….
FUNCTION
Display Digits…
FLOAT 6
Angle…….
RADIAN
ENTER Y=
WINDOW

8. Graph for in a [-5,5] by [-2,5] window:

9. Graph for in a [-5,5] by [-2,5] window:
Where is ?
Where is ?
Where is ?

10. Graph for in a [-5,5] by [-2,5] window:
Where is ?
What is the domain?
What is the range?
Where is ?
Where is ?

11. Population growth can often be modeled with an exponential function:
World Population:
million
Ratio:
The world population in any year is about times the previous year.
Nineteen years past 1991.
in 2010:
About 7.6 billion people.

12. Radioactive decay can also be modeled with an exponential function:
Suppose you start with 5 grams of a radioactive substance that has a half-life of 20 days. When will there be only one gram left?
After 20 days:
40 days:
t days:
In Pre-Calc you solved this using logs. Today we are going to solve it graphically for practice.

13. Y=
WINDOW
GRAPH

14. WINDOW GRAPH F5 5 46 days Upper bound and lower bound are x-values.
Math 5
Intersection
Use the arrow keys to select a first curve, second curve, lower bound and upper bound, and press ENTER each time.
46 days

15. e can be approximated by:
Many real-life phenomena can be modeled by an exponential function with base , where
e can be approximated by:
Graph:
y=(1+1/x)^x in a
[0,10] by [-5,10]
window.
Use “trace” to investigate the function.

16. We can have the calculator construct a table to investigate how this function behaves as x gets much larger.
TblSet
tblStart …….1000
ENTER
tbl………..1000
ENTER
ENTER
TABLE
Move to the y1 column and scroll down to watch the y value approach e. p