atan()
(PHP 4, PHP 5, PHP 7)
反正切
说明
atan(float $arg):float
返回$arg的反正切值，单位是弧度。atan()是tan()的反函数，它的意思是在atan()范围里的每个值都是a==tan(atan(a))。
参数
- $arg
要处理的参数
返回值
$arg的反正切弧度。
参见
Contrary to the current description, it should hold y == tan(atan(y)) for ALL y. However, x == atan(tan(x)) only holds for those x which are in the range of atan, which are those x with -pi/2 < x < pi/2. Of course, those equalities are limited by precision. On my machine tan(atan(1000)) returns 1000.0000000001. atan(tan(0)) returns 0 (correct). atan(tan(M_PI)) returns -1.2246467991474E-16 instead of 0.
to obtain the direction of the line, you are better to use the <? atan2((y2-y1)/(x2-x1)) ?> function, since the regular atan function will only return arguments in the half-plane, ie. if y2-y1 and x2-x1 are negative, atan will give you an angle measurement less than 90 degrees, while it really should be between 180 and 270
Arc Tan curve manipulation. I used this formula to help with increasing and then diminishing return for y given an increasing x for a game. Ie: Food production (output) is y. Food research is x. The more research you put into x the more you produce, however after a certain point you get less reward. y = atan(x - pi()) + pi()/2; The + pi()/2 moves it up the y axis so you'd add more if you want it to start higher. The x - pi() moves it to the right so you'd minus more to move it more. If you want stretched along the y axis change it to 2 * atan( ...... ) Dunno how useful it is... but it's there. Daz
arcctg function
function actg($arg){
return acos($arg/(sqrt(1 + $arg * $arg)));
}