Game Development Reference
In-Depth Information
Figure 12.4
Trigonometric notions arise from explorations of circles and coordinates.
the generalization of the situation Figure 12.5 provides, you can see you can
calculate the sine of
using the data you possess with the point (4,3). First you
calculate
r
, the hypotenuse. Then you find the ratio of
y
to
r
.
Degrees and Radians
When you first learn to relate an angle to a circle, your activity often begins with an
orientation toward the circle that begins with the Cartesian plane. As Figure 12.6
illustrates, you extend a line (
r)
from the center of a circle to its perimeter. Using
the standard form of an angle, you identify the
x
axis extending to the right
from the origin as the initial side of the angle. The line that creates the angle
constitutes the terminal side. You measure the angle (
) created by the initial side
and the terminal sides in degrees that describe the perimeter of the circle.
