Name
Math.cos( ) Method — compute the cosine of an angle
Availability
Flash 5; may be used when exporting Flash 4 movies
Synopsis
Math.cos(theta)
Arguments
- theta
An angle, in radians (not degrees), in the range 0 to 2π.
Returns
The cosine of theta
(the result is in the
range -1.0 to 1.0).
Description
The cos( )
function returns the trigonometric
cosine of an angle. In a right triangle, the cosine of an angle is
the result of dividing the length of the side adjacent to the angle
by the triangle’s hypotenuse.
Usage
Note that cos( )
expects angles to be provided
in radians, not degrees.
Example
trace (cos(0)); // Displays: 1.0 trace (cos(Math.PI)); // Displays: -1.0
The cos( )
function can be used along with
sin( )
to calculate a point on a circle, which
we use in the following example to move a movie clip in a circular
path. Given the radius of a circle, r, and an
angle, θ, measured counterclockwise from the positive horizontal
axis, a point’s location is (r*cosθ, r*sinθ):
// CODE ON FRAME 1
var radius = 100; // Radius of circle path var centerX = 275; // Horizontal center of circle path var centerY = 200; // Vertical center of circle path var rotAngleDeg = 0; // Angle of object in degrees, measured // counterclockwise from the horizon (x-axis) var rotAngRad; // Radian version of rotAngleDeg // Convert degrees to radians. There are 2*pi radians per 360 degrees. function degreesToRadians(degrees) { return (degrees/180) * Math.PI; }// CODE ON FRAME 2
// Increase the rotation angle by 5 degrees rotAngleDeg ...
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