arcsin with arduino

[gioscarab]

Hi guys. I am writing down a useful library for 2dof systems.
I am tryng to trasform servo angles in coordinates with sin(); and after computation I need to return to angles with arcsin(); but seems that arduino standard math library can't do it
Have some advices?

[system]

http://www.nongnu.org/avr-libc/user-manual/group__avr__math.html#ga98384ad60834911ec93ac5ae1af4cf0a

[mowcius]

asin()