Rockler's dedicated Technical Support Team reports that they've fielded more than the usual number of questions over the past few weeks on how to translate "rise and run" (the way that angles are described when you're talking about the pitch of a roof or a flight of stairs) into degrees. Here, compliments of Ellis Walentine and our friends at the Woodworker's Journal, is the answer:
Q. A DIYer has a question that involves geometry. He is cutting paneling to run along his stairs and is wondering if there is an easy way to calculate that angle.
Ellis Walentine: The easiest way is to run a very simple computation on a trig calculator. Actually, your computer probably has a trig calculator somewhere in the utilities folder. Just measure the rise and run between any two points on the slope. The quotient is the tangent of the included angle. Plug this into your calculator and it will tell you the precise angle (see drawing). The angle of your cuts on the bottom ends of your panel boards will be the complementary angle, or the difference between the included angles and 180 degrees.
From the Woodworker's Journal eZine 2001 Q & A archives
If the above has whet your appetite for more woodworking math info (or, has utterly confused you) you'll find more facts and figures - including a very basic trigonometry refresher - in Rockler's article, "Understanding Angles."