Game Development Reference
In-Depth Information
To examine relating the point to the differences of the values of two points,
consider that if you take the ratio shown in Figure 6.11, you develop this
equation. On the top, you present the ratio and the slope:
ð y 2 y 1 Þ
ðx 2 x 1 Þ ¼ m
ðy 2 y 1 Þ¼mðx 2 x 1 Þ
When you rewrite the equation in the second form, the result is known as the
point-slope equation . This equation gives a formal definition to the notion that if
you know the coordinates of a point on a line and the slope of the line, then you
can create an equation for the line.
Consider the line shown in Figure 6.12.
Figure 6.12
Two points allow you to create an equation.
 
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