arcus sinus function

i wont to write function that will calculate this:

b1=asn(a*c/b/d*m/vo)
asn is arcus sinus funcion

asn(x)=atn(x/sqr(-x*x+1))

i write it like this but it tell me error--->type mismash

function asn$(x)
d=atn(x/sqr(-x*x+1))*180/3.141592
asn$=str$(d)
end function

b1=asn$(a*c/b*m/vo)-------->what is wrong with this-->it tell me "duplicate definition" :mad:

help me please

Er...what are you coding in? If you are using VB.Net you can use the Math namespace.