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Arc Cosine

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Join Date: Sep 2005

Posts: 16

Reputation: grandfilth is an unknown quantity at this point

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grandfilth grandfilth is offline

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Arc Cosine

Oct 3rd, 2005

I've looked in a couple of books, and can't find this anywhere, i'm looking for the opposite of the cos funtion, i.e. I know the cos of the angle, and need to know the actual size of the angle, is there an implicit function? If not, how can I achieve the same result? Any help would be much appreciated...

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Join Date: Mar 2005

Posts: 464

Reputation: invisal is a jewel in the rough

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invisal

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Re: Arc Cosine

Oct 4th, 2005

try this function :

 Help with Code Tags 
 Visual Basic 4 / 5 / 6 Syntax (Toggle Plain Text) 
Public Function ArcCos(ByVal X As Double) As Double
    If X <> 1 Then
        ArcCos = Atn(-X / Sqr(-X * X + 1)) + 2 * Atn(1)
    Else
        ArcCos = 0
    End If
End Function
Public Function ArcCos(ByVal X As Double) As Double
    If X <> 1 Then
        ArcCos = Atn(-X / Sqr(-X * X + 1)) + 2 * Atn(1)
    Else
        ArcCos = 0
    End If
End Function

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Join Date: Sep 2005

Posts: 16

Reputation: grandfilth is an unknown quantity at this point

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grandfilth grandfilth is offline

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Re: Arc Cosine

Oct 5th, 2005

Thanks, i'll check if it works, how does it work?What's Atn?What's the theory behind it?Any help would be much appreciated, i'd like to understand you see...

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Join Date: Mar 2005

Posts: 464

Reputation: invisal is a jewel in the rough

Solved Threads: 49

invisal

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Re: Arc Cosine

Oct 5th, 2005

Atn is arctangent

let talk about math

tan(x) = sin(x) / cos(x)
cos(x) = sqr(1 - sin(x)^2)
tan(x) = sin(x) / sqr(1 - sin(x)^2)

so we got ArcSin = X / sqr(-X * X + 1)
and ArcCos = 90 - ArcSin
so ArcCos = (-X / sqr(-X * X + 1)) + 2 * Atn(1)