Game Development Reference
In-Depth Information
2. Click the Parens menu item. To position the parentheses, click to the right of
the minus sign. Pull the parentheses apart to allow for two fields and a minus
sign.
3. Click the Value menu item. Inside the parentheses in the lower equation
composition area, click to position the Value field. Type x in this field.
4. Now click the menu item for Subtract. To position the minus sign, click to
the right of the Value field.
5. Then click the Value menu item again, and place the corresponding field to
the right of the minus sign. Type 4 in the field.
6. Click the Power menu item. To position the Exponent field, click to the
upper right of the closing parenthesis. After you position the Exponent field,
type 2 in it.
7. Set the Zoom x axis value to
4 and the y axis value to
3.
8. To generate the graph, in the lower-right panel of Visual Formula, click the
Chart for Formula 2 button.
To the Left
As Figure 10.36 shows, the square of the sum of two values generates parabolas
that are shifted to the left of the
y
axis. Multiplying the sums by negative numbers
inverts the parabolas. The equations you employ to shift and generate parabolas of
this type work in the same fashion as the equations discussed in the previous
section. The difference is only that the parabolas are shifted to the left.
When you shift the parabolas to the left, you in essence subtract a negative value.
You can write the equation as
y ¼ðx ðbÞÞ
2
, but it is just as easy to write it in
the form you see depicted in Figure 10.36. When you multiply the sum by
1,
you invert the parabola.
To implement these two parabolas as shown in Figure 10.36, follow the steps in
the previous section. At Step 3 in the upper equation and at Step 4 in the lower
equation, instead of using a minus sign between the two fields within the par-
entheses, click the Add menu item and position the plus sign after the first Value
field.
