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 Last updated: Fri, 07 Jun 2013

# acos

(PHP 4, PHP 5)

acosАрккосинус

### Описание

float acos ( float `\$arg` )

Возвращает арккосинус числа `arg` в радианах. acos() - обратная тригонометрическая функция к cos(), т.е. a==cos(acos(a)) для каждого значения а, входящего в область значений функции acos().

`arg`

Аргумент функции

### Возвращаемые значения

Арккосинус числа `arg` в радианах.

### Смотрите также

• cos() - Косинус
• acosh() - Гиперболический арккосинус
• asin() - Арксинус
• atan() - Арктангенс

User Contributed Notes acos - [2 notes]
zoltan dot szentesi at nokia dot com
6 years ago
``` 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! :-) ```
-3
anthony at interiorgoodsdirect dot com
5 years ago
``` To calculate an angle from a triangle's sides. Use the 'law of cosines' : <?php //        a²+b²-c²            // 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. ```