asin

(PHP 3, PHP 4, PHP 5)

asin -- 反正弦

说明

float asin ( float arg )

返回 arg 的反正弦值,单位是弧度。asin()sin() 的反函数,它的意思是在 asin() 范围里的每个值都是 a==sin(asin(a))

参见 asinh(), acos()atan()


add a note add a note User Contributed Notes
pierre dot langlois at space dot gc dot ca
01-Jun-2005 09:22
The argument of asin is not in radians. asin returns radians but the argument is a unitless ratio

opposite side / Hypothenuse = sin (theta)
theta=asin(opposite side / Hypothenuse )