Defining A Function: Box With Lid - Texas Instruments TI-80 Manual Book

Defining a Function: Box with Lid

Take an 8½"×11" sheet of paper and cut X by X squares from two corners and X
by (X+B) rectangles from the other two corners. Now fold the paper into a box
with lid. What X would give the maximum volume V of a box made in this way?
Use tables and graphs to determine the solution.
Begin by defining a function that describes the
volume of the box.
From the diagram:
Substituting: V = (W – 2X) (L à 2 – X) X
If necessary, press z † Í to change the
MODE to FLOAT
return to the Home screen and clear it.
¿ ƒ
1. Press
8.5
the paper.
¿ ƒ
Press 11
the paper.
2. You define functions for tables and graphs on the
edit screen.
Press o to access this screen.
3. Enter the function for volume as
¹ @ ¤ £ ƒ
W 2
to define function
quickly without pressing ƒ.)
enter
X
The = sign is highlighted to show that
2X + A = W
2X + 2B = L
V = A B X
. Then press y . ' to
Í to store the width of
W
Í to store the length of
L
Y1
¥ ¹ @ ¤ @ Í
L 2
in terms of . (@ lets you
Y1 X
Y=
. Press £ ƒ
Y1 is selected.
X
W A
X B X
L
Getting Started 7
B