ActionScript for Flash MX: The Definitive Guide, Second Edition

Math.atan2() Method

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Returns

The angle, in radians, whose tangent is x.

Description

The arc tangent function (sometimes written as tan

-1

) is the inverse of the tangent func-

tion. It returns the angle whose tangent has the specified value, in radians. The return value

is in the range of –π/2 to π/2.

Example

trace (Math.atan(1.0)); // Displays: 0.78539...

trace (Math.atan(0.0)); // Displays: 0

trace (Math.atan(-Infinity)); // Displays: -1.5707... (i.e., -pi/2)

See Also

Math.acos( ), Math.asin( ), Math.tan( )

Math.atan2() Method

determine an angle based on a point

Flash 5; may be used when exporting Flash 4 movies

Math.atan2(y, x)

Arguments

y The y-coordinate of the point.

x The x-coordinate of the point.

Returns

The angle, in radians, of the point (x, y) from the center of a circle, measured counterclock-

wise from the circle’s positive horizontal axis (i.e., the X-axis). Ranges from π to -π.

(Negative values indicate angles below the X-axis).

Description

The atan2( ) method, like atan( ), performs an arc tangent calculation but uses x- and y-

coordinates, rather than their ratio, as arguments. That is, calculating an arc tangent with

atan2( ) as:

Math.atan2(9, 3); // Yields 1.24904577239825

is equivalent to calculating the arc tangent with atan( ), using the ratio ...