ASIN() function??

[Ketil Krumm]

I need to calculate the arc sine of a value, but PowerBASIC doesn't have an ASIN() function for this purpose.

Is there any way I can "emulate" ASIN() using the functions that are present?

Alternatively, does anyone know of a math library that has an ASIN() function?

Thanks,
Ketil

[Eric Pearson]

Disclaimer: My last Trig class was during the Cretacious Period (which was right after Third Period Study Hall) so I may be off-base here...

I wasn't aware that an ArcSin function was possible. Since each SIN value between 0 and 1 corresponds to two different angles, which one would it return? For example, the SINs of 45 and 135 are both (approx.) 0.71.

I believe that you would need both a SIN and a COS value (or at least a quadrant) to obtain an angle.

-- Eric

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[This message has been edited by Eric Pearson (edited May 11, 2000).]

[Vladimir Shulakov]

If I am not mistaken - that
PBDLL have ATN(), and

ASIN(L)=ATN(L/(SQR(1-L^2))

V.Shulakov



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[Ketil Krumm]

Eric,

Don't ask me, I'm just the programmer I took the economy route, and never used these functions.

Vladimir,

Thanks a million - your function works like a charm!! Using a scientific calculator as the definition of correct your function doesn't differ until the 5th to 7th decimal (depending on input value). This is well within what we can tolerate, and so our problem is solved. Thanks again!

Ketil

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