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# acos

(PHP 4, PHP 5)

acosArc cosine

### Описание

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.

### Список параметров

arg

The argument to process

### Возвращаемые значения

The arc cosine of arg in radians.

### Смотрите также

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 //        a�_+b�_-c�_            // 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! :-)```