Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site pucc-i Path: utzoo!watmath!clyde!burl!we13!ihnp4!inuxc!pur-ee!CS-Mordred!Pucc-H:Pucc-I:ags 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."