ActionScript for Flash MX: The Definitive Guide, Second Edition

Math.cos() Method

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Math.ceil(-5.5); // Returns -5

Math.ceil(3); // Returns 3

See Also

Math.floor( ), Math.round( )

Math.cos() Method

compute the cosine of an angle

Flash 5; can be used when exporting Flash 4 movies

Math.cos(theta)

Arguments

theta An angle, in radians (not degrees), normally in the range of 0 to 2π, although

any angle will suffice, as cosine is a periodic function.

Returns

The cosine of theta (the result is in the range of –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):

// Global Function: degreesToRadians()

// Converts degrees to radians. There are 2*pi radians per 360 degrees.

_global.degreesToRadians ...