# Sin taking negative values

**URL:** <https://forum.kirupa.com/t/sin-taking-negative-values/308187>\
**Category:** Uncategorized\
**Created:** [April 18, 2010, 6:33pm UTC](https://forum.kirupa.com/t/sin-taking-negative-values/308187 "2010-04-18T18:33:49Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![kod3](https://avatars.discourse-cdn.com/v4/letter/k/bbce88/32.png) [@kod3](https://forum.kirupa.com/u/kod3)\
**Post date:** [April 18, 2010, 6:33pm UTC](https://forum.kirupa.com/t/sin-taking-negative-values/308187/1 "2010-04-18T18:33:49Z")

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wat im trying to do is a simple thing… rotate 2 lines:ss and ss2 but using refraction index and a slider with minimum set to 0 and maximum to 90…the problem is that the sine value of the some angles between 0 and 90 are being negative  
anyone can help me on this?

ss.rotation= +slyda.value;  
var v:Number=Math.sin(slyda.value);  
trace(“v=”+v);  
var z:Number=v/1.33;  
ss2.rotation=+Math.asin(z);