Hey, gafftaper, I forgot to tell you I thought of you the other day while watching
The Colbert Report. Steven was going off a rant that included "There are only four countries today that don't use the metric
system: US, [something] [something] and Alaska!"
I had forgotten about the Shop Math section in Backstage Handbook. I just looked for my copy and of course can't find it. I've bought at least 4 friggin' copies of that
book, but someone always "borrows" it or I give a copy to someone more needy than myself. I'm now going to order two copies. Again!
I'll admit that I had to look up for verification the
EFL formula. There it was on the first
page of
Lighting the Stage, Art & Practise by Willard F. Bellman, where I had written it in 1980. Also written was the f-stop formula, which I've never used.
And speaking of looking up formulas that are never used. There is a typo in
Backstage Handbook (brown
cover). Expressing the quadratic formula, there's only a "-" sign after the "2ab". It should be a "±" (plus and/or minus) before the radical. At the time, I believe I called for a global recall, but never received a corrected copy. If I remember right, it IS correct in the blue
cover edition.
A free white
china marker to the first respondent who can demonstrate a real-world purpose for the quadratic equation!
Call now, operators are standing by.
I swear it's a conspiracy by educators who make these things up just so they have something to teach and grade students. Unlike deriving a lighting
fixture's multiplication factor from its
beam angle using trigonometry: [Excel format] Multiplying Factor(MF) =2*TAN((x/2)*PI()/180), where x is the
beam angle in degrees. BTW, the "*PI()/180" is just to force Excel to
express the answer in degrees rather than radians, and therefore isn't needed if calculating by
hand.