Texas Instruments TI-82 STATS - Defining a Function: Box with Lid

Getting Started 9
82STAT~1.DOC TI-83 international English Bob Fedorisko Revised: 10/27/05 1:33 PM Printed: 10/27/05 3:30
PM Page 9 of 18
Take a 20 cm. × 25 cm. sheet of paper and cut X × X squares from two corners. Cut
X × 12.5 cm. rectangles from the other two corners as shown in the diagram below.
Fold the paper into a box with a lid. What value of X would give your box the
maximum volume V? Use the table and graphs to determine the solution.
Begin by defining a function that describes the
volume of the box.
From the diagram: 2X + A = 20
2X + 2B = 25
V = A B X
Substituting: V = (20 N 2X) (25à 2 N X) X
1. Press o to display the Y= editor, which is
where you define functions for tables and
graphing.
2. Press £ 20 ¹ 2 „ ¤ £ 25 ¥ 2 ¹
„ ¤ „ Í to define the volume
function as
Y1 in terms of X.
„ lets you enter X quickly, without
having to press ƒ. The highlighted
= sign
indicates that
Y1 is selected.
Defining a Function: Box with Lid
20
A
X
X B X B
25