arc cosine function

[dee2dum]

Hi-

I'm trying to write a calculation function using arc cosine. Unfortunately, I haven't been able to find it. I've been able to find arc tangent, so thought that maybe arc cosine also existed in FM. Am I assuming incorrectly?

If the arc cosine function does not exist, does anyone know how I could still use the same formula with the provided functions?

[danjacoby]

As I recall from my schoolboy days (which were quite a while ago), the arccos of a number is the inverse of the cosine (i.e. 1/cos). If this is true, and since Cos(number) exists, how about a calc field that equals 1 / Cos(number)?

[dee2dum]

Thanks for the reply danjacoby, but unfortunately arccosine is not the same as 1/cos(number). 1/cos(number) is actually sec(number). I wish they were the same though because it would make my life a lot easier.

[slstrother]

The calc you need was posted on another forum.

Look Here

[LiveOak]

Arc cosine is the inverse cosine, but this isn't equal to 1/cosine.

-bd

[LiveOak]

Had to get back to my office and pull out the CRC Math Handbook:

Arccos x = pi/2 - Arctan (x/SQRT(X**2 + 1)) for all values of x.

Arccos x = Arctan (SQRT(1 - x**2)/x) for x >= 0

-bd

[danjacoby]

Wups -- got it. Arccos(X) is the number whose cosine is X?

As I said, it's been a long time since my schoolboy days -- and the memory is the second thing to go.

Don't ask.