Defining A Function: Box With Lid - Texas Instruments TI-82 STATS Manual Book

Defining a Function: Box with Lid

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:
Substituting:
1. Press o to display the
where you define functions for tables and
graphing.
2. Press £ ¹
20 2
„ ¤ „ Í to define the volume
function as in terms of
Y
1
„ lets you enter
having to press ƒ. The highlighted
indicates that
Y
1
2X + A = 20
2X + 2B = 25
V = A B X
V = (20 N 2X) (25à 2 N X) X
editor, which is
Y=
„ ¤ £ ¥
25
.
X
quickly, without
X
is selected.
X
20 A
X
¹
2
sign
=
B X B
25
Getting Started 9