>Hey all
>
>I've been trying to use the third formula on this page:
>
>http://en.wikipedia.org/wiki/Great-circle_distance
>
>The formula is unnamed, but is indicated as being the most accurate.
>
>My trig is pretty rusty, and I don't think I ever did it on a sphere. :)
>
>I'm plugging in the sample lat-long for BNA and LAX and I'm not getting the same results.
>
>I've converted everything to radians. They name a formula in the "worked example" but that name is not referenced elsewhere on the page, so I'm not even sure which formula they're trying to demonstrate.
>
>Can anyone show me what I'm missing?
>
>Thanks!
>
>

CLEAR
>SET DECIMALS TO 5
>
>m.lat1 = 36.12
>m.long1 = -86.67(SIN(m.rlat1) * SIN(m.rlat2)) + (COS(m.rlat1) * COS(m.rlat2) * COS(m.rDeltaLong))
>?"lat1",m.lat1,"long1",m.long1
>
>[snip]
>
>m.DeltaSigma = ;
>  atan( ;
>    SQRT(;
>      (COS(m.rlat2) * SIN(m.rDeltaLong))^2 + ;
>      (COS(m.rlat1) * SIN(m.rlat2) - SIN(m.rlat1) * COS(m.rlat2) * COS(m.rDeltaLong))^2;
>    ) ;
>    / ;
>      (SIN(m.rlat1) * SIN(m.rlat2)) + (COS(m.rlat1) * COS(m.rlat2) * COS(m.rDeltaLong)) ;
>  )
>
>return m.DeltaSigma

I think in the denominator you've prematurely closed the parenthesis after SIN(m.rlat2). The denominator line should be

(SIN(m.rlat1) * SIN(m.rlat2) + COS(m.rlat1) * COS(m.rlat2) * COS(m.rDeltaLong))