I want to use the spherical law of cosine formula, θ = atan2( sin Δλ ⋅ cos φ2 , cos φ1 ⋅ sin φ2 − sin φ1 ⋅ cos φ2 ⋅ cos Δλ ), to calculate distances between coordinates, but, I cannot for the life of me remember what the 'a' stands for.

Can some please help me out?

  • 3
    atan is arctangent. The a is not a stand-alone multiplier, atan is all one word. See this. – Jason Scheirer Jun 18 '14 at 14:14

'atan' is short for arctangent, or inverse tangent. Here is the Excel explanation of the ATAN2 function (since you used the Excel tag), and a detailed look at ways to implement the calculation.


I assume you're referring to the 'a' in front of the 'tan'. It's not a variable, 'atan' is the arctangent or inverse tangent.

Another form for same, in mathematics, is this: tan-1

  • Okay awesome im just used to seeing Arctan not atan @wxmacman – user32496 Jun 18 '14 at 14:27

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