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acos

(PHP 4, PHP 5)

acosArc cosine

Description

float acos ( float \$arg )

Returns the arc cosine of arg in radians. acos() is the complementary function of cos(), which means that a==cos(acos(a)) for every value of a that is within acos()' range.

Parameters

arg

The argument to process

Return Values

The arc cosine of arg in radians.

See Also

User Contributed Notes
acos
anthony at interiorgoodsdirect dot com
05-Dec-2007 01:28
```To calculate an angle from a triangle's sides. Use the 'law of cosines' : <?php //        aÂ_+bÂ_-cÂ_            // cosC = -------- //           2ab function calculateAngle(\$c,\$a,\$b) {     \$angleInRadians=acos((pow(\$a,2) + pow(\$b,2) - pow(\$c,2)) / (2 * \$a * \$b));     return rad2deg(\$angleInRadians); } ?> \$a, \$b, \$c are the triangle sides. The function returns the angle opposite side c, in degrees.```
zoltan dot szentesi at nokia dot com
06-Aug-2006 10:29
```Wondering what is the use of 'acos' function? It is essential in games, animations and drawings to determine the location of two objects relating to each other. To the point: the angle of two vectors is calculated by            v1X*v2X + v1Y*v2Y   acos(--------------------------)=angle between two vectors.                |v1| * |v2|  |v1| and |v2| are the length of the vectors and calculated using Pithagoras-formula: |v1|=sqrt(v1X*v1X + v1Y*v1Y) This helped me to calculate and share given space for 'n' amount of objects so that they don't overlap. Enjoy! :-)```