Defining A Function: Box With Lid - Texas Instruments TI-83 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: 2X + A = 20
Substituting:
1. Press o to display the
where you define functions for tables and
graphing.
2. Press £ ¹
20
„ ¤ „ Í to define the
volume function as
„ lets you enter
having to press ƒ. The highlighted
sign indicates that
2X + 2B = 25
V = A B X
V = (20 N 2X) (25à 2 N X) X
editor, which is
Y=
„ ¤ £
2 25
in terms of
Y
1
quickly, without
X
is selected.
Y
1
20 A
¥ ¹
2
.
X
=
X
X B X
25
Getting Started 9
B