You can also use your computer calculator, just set it on scientific mode.
Type in: (12.5 tan/45 cos) tan-1 = 17.4074…
In order to get the tan-1, first click “Inv” and then you’ll find “tan-1”
I used to be an estimator for a log house manufacturer before I became their export manager. Calculating odd shaped surfaces and volumes was the norm.
Unfortunately, I didn’t have that formula at the time. This would have saved me quite some time over the years instead of making 3D drawings by hand :shock:
OK, the first part, 12.5 tan/45 cos gives a result of 0.313523589615374
Then what do I do?
Ken
Depending on your calculator you take the Inverse Tangent or sometimes referred to as ARCTAN of that number. Usually listed as either ATAN or Tan-1 on most calculators.
You can type/click everything in at the same time
“(” then “12.5” then “tan” then “/” then “45” then “cos” then “)” then “inv” then “tan-1” then “=”
or
you take the number “0.313523589615374” then click “inv” then “tan-1”
That is with the computer’s calculator on the scientific mode. The one on my “real” calculator is different I have to press “shift” to get to the Arctan.
As Randy said, it could be listed as ATAN or Tan-1 and even Atn depending on the calculator.
aside from “tan”, all I have is “tanh” and that didn’t seem to work. I’m using the scientific calculator on my I-phone.
OK, now that I know what calculator you are using 
Type this, exactly as I write it:
(12.5tan/45cos)2nd tan-1=
On the iPhone4, the “2nd” key is on the top left
Hope this helps!
Got it! Thanks Will.