atan

(PHP 4, PHP 5, PHP 7, PHP 8)

atan — 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

tan() - 正切
atanh() - 反双曲正切
asin() - 反正弦
acos() - 反余弦

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User Contributed Notes 4 notes

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Anonymous ¶

7 years ago


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.

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darren_wheatley at hotmail dot com ¶

18 years ago


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

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joelperr at kiwi-interactif dot com ¶

16 years ago


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

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-7

Ts.Saltan ¶

6 years ago


arcctg function

function actg($arg){
    return acos($arg/(sqrt(1 + $arg * $arg)));
}

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官方地址：https://www.php.net/manual/en/function.atan.php

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atan

说明

参数

返回值

参见

User Contributed Notes 4 notes