這個方法返回其參數商數的反正切。該ATAN2方法返回-pi和PI 較(x,y)點的角度theta之間的數值。
語法
Math.atan2( x, y ) ;
下面是參數的詳細信息:
返回值:
返回一個數弧度的反正切值
Math.atan2( ±0, -0 ) returns ±PI. Math.atan2( ±0, +0 ) returns ±0. Math.atan2( ±0, -x ) returns ±PI for x < 0. Math.atan2( ±0, x ) returns ±0 for x > 0. Math.atan2( y, ±0 ) returns -PI/2 for y > 0. Math.atan2( ±y, -Infinity ) returns ±PI for finite y > 0. Math.atan2( ±y, +Infinity ) returns ±0 for finite y > 0. Math.atan2( ±Infinity, +x ) returns ±PI/2 for finite x. Math.atan2( ±Infinity, -Infinity ) returns ±3*PI/4. Math.atan2( ±Infinity, +Infinity ) returns ±PI/4.
例子:
<html> <head> <title>JavaScript Math atan2() Method</title> </head> <body> <script type="text/javascript"> var value = Math.atan2(90,15); document.write("First Test Value : " + value ); var value = Math.atan2(15,90); document.write("<br />Second Test Value : " + value ); var value = Math.atan2(0, -0); document.write("<br />Third Test Value : " + value ); var value = Math.atan2(+Infinity, -Infinity); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html>
這將產生以下結果:
First Test Value : 1.4056476493802698 Second Test Value : 0.16514867741462683 Third Test Value : 3.141592653589793 Fourth Test Value : 2.356194490192345