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Tony, you wrote: "It works!!"

Yes, these are tricks for getting an atan2 function out of a calculator. The pol function is the same thing. But do you understand how to do this with the straight tan function? You should take note of the numerator and denominator separately when you set up the standard calculation. Then there is a simple rule for determining the quadrant (determining whether you have to add 180° or not) based on the algebraic signs of the two parts. I'll leave it to you to learn the rule and understand why it works. That's all you have to do to get this right using the standard tan function. And in fact that's what the pol function on the calculator is doing. There's no magic to this, and there's no need to learn all sorts of arcane features of your calculator turning you into some sort of calculating robot. If you intend to work with this particular formula for azimuth, then this is something that you should really know about tangents and arctangents. It shouldn't be buried in some mysterious keypunching on your calculator.

Frank Reed