# Kathryn Bollinger's TI-83/84 Calculator Help in MATH 142

Finding an Exact Fractional Value of a Decimal
From your home screen, if you have calculated a value which is not an integer value, you can determine whether or not it is a rational number and can be written as an exact fraction by hitting MATH and choosing option 1: Frac and then hitting ENTER. The reduced fraction for your value should appear if it is a rational number.

Finding Function Values
1. Enter your function into Y=.
2. Return to the home screen by pressing 2nd MODE (QUIT).
3. Call your function to the home screen by pressing VARS, cursoring right to Y-VARS, selecting 1:Function, and choosing the appropriate function name.
4. You will now have your function name on the screen, say Y1.
5. Add parenthesis and an x-value, just as function notation would be written on paper, so that you have something like Y1(2).
Finding the Intersection Point of Two Lines
1. Graph the two functions by entering the slope-intercept form of the lines into Y1 and Y2. These are located under the Y= button.
2. Go to CALC which is found by pressing 2nd TRACE.
3. Select option 5:intersect.
4. The calculator will prompt you for the first and second curves you want to intersect. The cursor will blink on a function and show the function name in the upper left corner of the screen. When it blinks on Y1, press ENTER & when it blinks on Y2, press ENTER.
5. The calculator will then ask you to guess where the intersection point is located. Use your right and left arrow keys to move to the intersection point and press ENTER.
6. The intersection point will appear at the bottom of the screen.
Finding the Zeros of a Quadratic Function
• Using Intersections
1. Put your quadratic function into Y1 and set Y2=0. (You can use any two function locations.)
2. Find the intersection points of these two functions using the directions given above.

• Using the Zero Function
1. Put your quadratic function into Y1 (or any other function location).
2. Graph the function so that you can see where the quadratic crosses the x-axis (where your function = 0).
3. Go to CALC which is found by pressing 2nd TRACE.
4. Select option 2:zero.
5. The calculator will prompt you for the LeftBound. Use your left or right arrow key to move the cursor to the left of where it crosses and hit ENTER. The calculator will then prompt you for the RightBound. Move the cursor to the right of where it crosses and hit ENTER.
6. The zero will appear at the bottom of the screen.
Compound Interest and Effective Rates of Interest for Non-Continually Compounded Accounts
For both of these types of problems, go to FINANCE on your calculator. If you have the regular TI-83, this is found by hitting 2nd x^(-1). If you have the TI-83 Plus, this is found by hitting the blue APPS button and selecting option 1:Finance....

• Compound Interest
1. Select option 1:TVMSolver. You should have the following on your screen:

N =
I%=
PV=
PMT=
FV=
P/Y=
C/Y=

2. Fill in all but one of the above options (the one you are trying to solve for) as follows: N = the total number of times compounded (the number of times compounded per year times the number of years), I% = interest rate (not in decimal form), PV = present value (the amount you invest), PMT = 0 (we are not making payments in this class), FV = future value (the amount of money you have at the end of your investment), P/Y = C/Y = the number of times compounded per year (since we are not making payments). If you fill in PV and FV, one must be negative in order for your calculator to find an answer. (Simulating the flow of money between you and the bank.) Make sure you have some kind of value entered in the spot for whichever variable you are solving for or else the calculator will not let you proceed to input values for the rest of the variables.
3. Move your cursor to the value you are solving for and hit ALPHA and then ENTER.

• Effective Rates of Interest
1. Select option C:Eff(.
2. Input the nominal interest rate (not in decimal form) followed by a comma and then the number of times the account is compunded per year.
3. Hit ENTER.

Evaluating Definite Integrals
1. Go to MATH and select option 9:fnInt.
2. Fill in the four arguments for fnInt as follows: fnInt (function, X, lower limit, upper limit)
3. Hit ENTER.