inverse secant function

[kchewy80]

I am trying to use the inverse secant formula given in the help menu but I keep getting the wrong answer. Here is what I am using:

angle(i) = Atn(a / Sqr(a * a - 1)) + _
Sgn((a) - 1 * (2 * Atn(1))
angle(i) = angle(i) * 180 / PI

When a is 1.414 the angle is calculated to be 172 degrees, when it should be 45 degrees.

Any ideas on why this is would be very helpful.

Thanks

 

[Zathras]

Try this:
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Option Explicit
Const RADIANS_TO_DEGREES = 57.2957795130823

Function ArcSecant(A)
  ArcSecant = (Sgn(A) * Atn(Sqr(1 / (A ^ 2 - 1)))) * RADIANS_TO_DEGREES
End Function

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Or if you prefer, here is the equivalent in a spreadsheet function:
[blue]

  =(SIGN(A1)*ATAN(SQRT(1/(A1^2-1))))*180/PI()

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