acos

(PHP 4, PHP 5)

acos — 反余弦

说明

float acos ( float $arg )

返回 arg 的反余弦值，单位是弧度。acos() 是 cos() 的反函数，它的意思是在 acos() 范围里的每个值都是 a==cos(acos(a)) 。

参见 acosh(), asin() 和 atan()。

PHP手册 - N: 反余弦

用户评论:

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 11:29)

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! :-)