I prefer seeing math formulas written out with full notation so there's less chance of confusion. I also like seeing formulas derived in steps so the reader can see how it works.

In this case, the author made a mistake. The "π/180" term converts "degree" into "radian", there's no reason for it to be there. I don't know how he got "34.8" degrees.

To keep it simple, you can just measure "h" and "w" then use the calculator to get ARCTAN.

As always, please check my math (drawing is not to scale)

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