Download Calculator Notes for the Casio fx

DA2_FX7400G_07.qxd 11/30/2005 04:27 PM Page 44
CHAPTER 7
Calculator Notes for the fx-7400G Plus
Note 7A • Function Notation
Functions are usually entered from GRAPH mode and are referred to by
name as Y1, Y2, . . . , Y9, Y10.
To evaluate a function for a particular x-value, for example, Y1 when x 4,
enter RUN mode. Press 4 → , EXE to assign a value of 4 to x. Then, press
VARS ˛ F2 (GRAPH) F1 (Y) 1 EXE to see the value of Y1.
Note 7B • Some Functions
To use the command for squaring, in RUN mode, enter a number and
press X2 EXE .
To use the command for square root, press
enter a number and press EXE .
SHIFT [ ]
in RUN mode. Then
To use the command for the sum of a list, in RUN mode press
OPTN F1 (LIST) ˛ ˛ F2 (Sum). Then, press SHIFT [ { ] and enter the numbers
in the list, separating each number with a comma. Close the braces and
press EXE .
Alternatively, from either RUN or STAT mode, enter numbers into a list, for
example, List 1. (See Note 1B.) Then, on the Run screen, enter “sum List 1”
by pressing OPTN F1 (LIST) ˛ ˛ F2 (Sum) ˛ F1 (List) F1 (List) 1 EXE .
The command for random number generates a random ten-digit
decimal number between 0 and 1. From RUN mode, press
OPTN F4 (PROB) F4 (Ran#) EXE .
Note 7C • Absolute Value
To find the absolute value of a number, from the Run screen, press
OPTN ˛ F1 (NUM) F1 (Abs). Then, enter a number and press EXE .
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fx-7400G Plus
Note 7D • Friendly Windows
When you trace a function or locate a point on the screen, you often see
long, “ugly” decimal values for the coordinates of your points. Sometimes,
however, the values are “nice, friendly” values, like 2.4 or 4.84, or repeating
decimals, like 4.3333333.
When the proper values are set for Xmin and Xmax in the View Window
screen, the coordinate values of your points will be “friendly” numbers for
most functions. This is because the calculator screen is made of tiny square
dots called pixels, and when you move horizontally across the screen, the
x-coordinate changes by one pixel with each trace step. When the total
number of pixels across the screen (78 pixels) is either equal to, or a multiple
of, the breadth of the domain, Xmax – Xmin, the window will be “friendly.”
For example, if Xmin 0 and Xmax 78 or Xmin 1 and Xmax 8.8, the
window will be friendly. (Note: The y-coordinate is calculated by evaluating
the function for the x-coordinate. So if the coefficients in a function are
irrational, the y-coordinates will not be nice even in a friendly window.)
Two Friendly Square Windows
If you press SHIFT [V-Window] F1 (INIT), you get a special type of small
friendly window, called a friendly square window. It is friendly because it has
the view window values [3.9, 3.9, 1, 2.3, 2.3, 1]. It is square because the
horizontal and vertical scales on the screen are equal in size. In a square
window, circles appear symmetric and round, and the line y x makes a
45-degree angle with both axes. A square window is often the preferred
window to use because it displays no visual distortion. However, this
window, [3.9, 3.9, 1, 2.3, 2.3, 1], is sometimes too small to show much
of the graph.
[3.9, 3.9, 1, 2.3, 2.3, 1]
To see more of the graph in the window, you can double the Xmin, Xmax,
values to [7.8, 7.8, 1, 4.6, 4.6, 1]. This square window is
referred to as the friendly window with a factor of 2.
Ymin, and Ymax
[7.8, 7.8, 1, 4.6, 4.6, 1]
(continued)
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Note 7D • Friendly Windows (continued)
fx-7400G Plus
The friendly window with a factor of 2 is often a convenient window to use.
To save it and recall it quickly, follow these steps.
a. First, enter the values [7.8, 7.8, 1, 4.6, 4.6, 1] into your View
Window screen.
b. From the View Window screen, press
F3 (Sto).
c. The next time you need this window—for example, for the graph of
y x 2—press SHIFT [V-Window] F4 (Rcl).
[10, 10, 1, 10, 10, 1]
[7.8, 7.8, 1, 4.6, 4.6, 1]
Other Friendly Square Windows
To assure that a window is square, the size of a horizontal step, called x,
must equal the size of a vertical step, called y. x is the step size of the
trace. In the square window [3.9, 3.9, 1, 2.3, 2.3, 1], x is 0.1. In the
square window [7.8, 7.8, 1, 4.6, 4.6, 1], x is 0.2.
Values for origin-centered friendly square windows are
[39 x, 39 x, 1, 23 y, 23 y, 1]. For example,
if x and y equal 0.3, then . . .
First-quadrant friendly square window values are [0, 78 x, 1, 0, 46 y, 1].
Again, if x and y equal 0.3, then . . .
[0, 23.4, 1, 0, 13.8, 1]
(continued)
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Note 7D • Friendly Windows (continued)
fx-7400G Plus
Friendly Windows That Are Not Square
The Ymin and Ymax values of a friendly window can be changed to
show a larger or smaller range. The graph will look distorted and it will
no longer be square, but this might be necessary to see more of the
graph. For example, the graph of y x 2 in the friendly square window
[7.8, 7.8, 1, 4.6, 4.6, 1] runs off the top of the graph for x-coordinates
greater than 2. If you want to see more of the graph, change the window
to [7.8, 7.8, 1, 10, 100, 10]. This is a friendly window because the
coordinates are still nice, but it is not square.
[7.8, 7.8, 1, 4.6, 4.6, 1]
[7.8, 7.8, 1, 10, 100, 10]
You can also see more of a graph without first changing the view window
settings. Without using the trace option, use the arrow key to automatically
scroll the graph in any direction. As you scroll, the view window settings
change to reflect the current screen.
©2007 Key Curriculum Press
Discovering Algebra Calculator Notes for the Casio fx-7400G Plus
47