atan

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

atan — Arc tangente

Descripción

atan(float $num): float

Se devuelve el arcotangente de num, en radianes. atan() es la función inversa de tan(), lo que significa que $num == tan(atan($num)) para cada valor de num que se encuentra en el dominio de la función atan().

Parámetros

num: El argumento a tratar

Valores devueltos

El arcotangente de num, en radianes.

Ver también

tan() - Tangente
atanh() - Arco tangente hiperbólica
asin() - Arc sinus
acos() - Arc coseno

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User Contributed Notes 1 note

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Anonymous ¶

10 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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