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From: ags@pucc-i (Seaman)
Newsgroups: net.math
Subject: Re: need help
Message-ID: <170@pucc-i>
Date: Wed, 1-Feb-84 09:53:04 EST
Article-I.D.: pucc-i.170
Posted: Wed Feb  1 09:53:04 1984
Date-Received: Tue, 7-Feb-84 10:30:20 EST
References: <6686@mgweed.UUCP>
Organization: Purdue University Computing Center
Lines: 27

>  Perhaps some math whiz can help me out with a problem.
>  I have a computer program that gives me an answer that is
>  the sin of x. How can I get the value of x without an
>  arc-sin function? My computer just has sin, cos, tan
>  and arc-tan. (I also have the formula ACS(x)=-ATN(x/sqr(-x*x+1))+pi/2
>  which gives me the arc-cosine function).
>  
>  Tnx  Bob

If y = sin(x) and

   -PI/2 < x < PI/2

then cos(x) = sqrt(1-sin^2(x)) = sqrt(1-y^2)

and tan(x) = sin(x) / cos(x) = y / sqrt(1-y^2)

so that arcsin(y) = x = arctan(y/sqrt(1-y^2))


-- 

Dave Seaman
..!pur-ee!pucc-k:ags

"Against people who give vent to their loquacity 
by extraneous bombastic circumlocution."