# Re: [Flightgear-devel] Plea for help: geometry/trigonometry problem

`On Wed, 03 Nov 2004 16:17:24 -0600, Jon S Berndt <[EMAIL PROTECTED]> wrote:`
```
> Maybe I am missing what you are trying to do, but I just tried this in
> Excel:
>
> -atan2(theta,phi)
>
> which gives this:
>
> theta   phi             angle (from forward, positive clockwise)
> 45      0               0
> 45      -45             45
> 0       -45             90
> -45     -45             135
> -45     0               -180
> -45     45              -135
> 0       45              -90
> 45      45              -45
>
> 10      0               0
> 10      80              -82.87498365
> 80      10              -7.125016349

Those look pretty reasonable for offsets from the aircraft's current
heading.  For example, if you're at 0 pitch a 45 degree right bank,
uphill will be 90 degrees to the left of your current heading (-90).
If you're pitched down 45 degrees and banked 45 degrees to the right,
uphill will be 135 degrees to the left of your current heading; and so
on.

All the best,

David

--
http://www.megginson.com/

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