31
G
RAPHING
T
ECHNOLOGY
G
UIDE
: TI-82
Copyright © Houghton Mifflin Company. All rights reserved.
: -B/(2A) → R (-) ALPHA B ÷ (2 ALPHA A) STO➧ ALPHA R ENTER
calculates the real part
2
b
a
−
of the complex roots
: Disp R PRGM ► 3 ALPHA R ENTER
: Disp “IMAGINARY PART” PRGM ►
3 2nd A-LOCK " I M A G I N A R Y
O
P A R T "
ENTER
:
–D/(2A) → I 2nd (-) ALPHA D ÷ (2 ALPHA A) STO➧ ALPHA I
ENTER
calculates the imaginary part
2
D
a
−
of the complex roots;
since D < 0, we must use –D as the radicand
: Disp 1 PRGM ► 3 ALPHA I ENTER
: End PRGM 7 ENTER
marks the end of an If-Then-Else group of commands
: End PRGM 7
When you have finished, press 2nd QUIT to leave the program editor.
You may remove a program from memory by pressing 2nd MEM 2 [Delete...] 6 [Prgm...]. Then move the cursor
to the program’s name and press ENTER to delete the entire program.
2.10.2 Executing a Program: To execute the program just entered, press PRGM and then the number or letter that
it was named. If you have forgotten its name, use the arrow keys to move through the program listing to find its
description QUADRAT. Then press ENTER to select this program and enter again to execute it.
The program has been written to prompt you for values of coefficients a, b, and c in a quadratic equation ax
2
+ bx +
c = 0. Input a value, then press ENTER to continue the program.
If you need to interrupt a program during execution, press ON.
The instruction manual for your TI-82 gives detailed information about programming. Refer to it to learn more
about programming and how to use other features of your calculator.
2.11 Differentiation
2.11.1 Limits: Suppose you need to find this limit:
0
sin 4
lim
x
x
x
→
. Plot the graph of f (x) =
sin 4x
x
in a convenient
viewing rectangle that contains the point where the function appears to intersect the line x = 0 (because you want the
limit as x → 0). Your graph should lend support to the conclusion that
0
sin 4
lim
x
x
x
→
= 4.
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