28
G
RAPHING
T
ECHNOLOGY
G
UIDE
: TI-82
Copyright © Houghton Mifflin Company. All rights reserved.
Figure 2.76: Polar graph of r = 4sin θ
Figure 2.76 shows rectangular coordinates of the cursor’s location on the graph. You may sometimes wish to trace
along the curve and see polar coordinates of the cursor’s location. The first line of the WINDOW FORMAT menu
(Figure 2.18) has options for displaying the cursor’s position in rectangular RectGC or polar PolarGC form.
2.9 Probability
2.9.1 Random Numbers: The command Rand generates a number between 0 and 1. You will find this command in
the PRB (probability) sub-menu of the MATH menu. Press MATH ◄ 1 ENTER to generate a random number.
Press ENTER to generate another number; keep pressing ENTER to generate more of them.
If you need a random number between, say, 0 and 10, then press 10 MATH ◄ 1 ENTER. To get a random number
between 5 and 15, press 5 + 10 MATH ◄ 1 ENTER.
2.9.2 Permutations and Combinations: To calculate the number of permutations of 12 objects taken 7 at a time,
12
P
7
,
press 12 MATH ◄ 2 7 ENTER. Thus
12
P
7
= 3,991,680, as shown in Figure 2.77.
Figure 2.77:
12
P
7
and
12
C
7
For the number of combinations of 12 objects taken 7 at a time,
12
C
7,
press 12 MATH ◄ 3 7 ENTER. So
12
C
7
=
792.
2.9.3 Probability of Winning: A state lottery is configured so that each player chooses six different numbers from 1
to 40. If these six numbers match the six numbers drawn by the State Lottery Commission, the player wins the top
prize. There are
40
C
6
ways for the six numbers to be drawn. If you purchase a single lottery ticket, your probability
of winning is 1 in
40
C
6
. Press 1 ÷ 40 MATH ◄ 3 6 ENTER to calculate your chances, but don’t be disappointed.
2.10 Programming
2.10.1 Entering a Program: The TI-82 is a programmable calculator that can store sequences of commands for later
replay. Here’s an example to show you how to enter a useful program that solves quadratic equations by the
quadratic formula.
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