# Comment about Math#asin

**URL:** <https://www.ruby-forum.com/t/comment-about-math-asin/126819>\
**Category:** Development\
**Created:** [January 22, 2008, 3:30pm UTC](https://www.ruby-forum.com/t/comment-about-math-asin/126819 "2008-01-22T15:30:05Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [January 22, 2008, 3:30pm UTC](https://www.ruby-forum.com/t/comment-about-math-asin/126819/1 "2008-01-22T15:30:05Z")

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e$B1sF#$H?=$7$^$9!#e(B

Math#asin e$B$O%3%a%s%H$K$h$k$He(B 0…PI  
e$B$NCM$rJV$9$3$H$K$J$C$F$$$^$9$,e(B  
e$B\<B:]$K$Oe(B -{PI/2} … {PI/2} e$B$@$H;W$$$^$9!#e(B

# e$B8H$_$?$$$J%D%C%3%_$P$+$j$G$9$\_$^$;$se(B (e$B\>Pe(B)

# Index: math.c

— math.c (revision 15174)  
+++ math.c (working copy)  
@@ -128,7 +128,7 @@

- call-seq:
- 

```
Math.asin(x) => float

```

- 

- 
  - Computes the arc sine of _x_. Returns 0…PI.

- 
  - Computes the arc sine of _x_. Returns -{PI/2} … {PI/2}.  
\*/

static VALUE

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [January 23, 2008, 4:50am UTC](https://www.ruby-forum.com/t/comment-about-math-asin/126819/2 "2008-01-23T04:50:33Z")

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e$B$^$D$b$He(B e$B$f$-$R$m$G$9e(B

In message “Re: [ruby-dev:33276] comment about Math#asin”  
on Tue, 22 Jan 2008 23:28:05 +0900, “Yusuke ENDOH” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|Math#asin e$B$O%3%a%s%H$K$h$k$He(B 0…PI e$B$NCM$rJV$9$3$H$K$J$C$F$$$^$9$,e(B  
|e$B\<B:]$K$Oe(B -{PI/2} … {PI/2} e$B$@$H;W$$$^$9!#e(B  
|  
|# e$B8H$_$?$$$J%D%C%3%_$P$+$j$G$9$\_$^$;$se(B (e$B\>Pe(B)

e$B$$$($$$(!"=u$+$j$^$9!#%3%\_%C%H$7$F$$$?$@$1$^$;$s$+!)e(B

---

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [January 23, 2008, 5:15am UTC](https://www.ruby-forum.com/t/comment-about-math-asin/126819/3 "2008-01-23T05:15:05Z")

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At Tue, 22 Jan 2008 23:28:05 +0900,  
Yusuke ENDOH wrote:

> é è—¤ã¨ç”³ã—ã¾ã™ã€‚
> 
> Math#asin はコメントによると 0…PI の値を返すことになっていますが  
> 実際には -{PI/2} … {PI/2} だと思います。

　ruby\_1\_8 ブランチについてもお願いします。