View Single Post
  #17   Report Post  
Posted to rec.woodworking
Greg Guarino[_2_] Greg Guarino[_2_] is offline
external usenet poster
 
Posts: 1,200
Default For you math wizards

On 4/15/2013 2:47 PM, Doug Miller wrote:
"Gramp's shop" wrote in news:384921f5-292d-40cc-9e3e-
:

I need to draw an arc for a piece of trim. The end points of the arc are 5 feet apart and the

depth of the arc at the center point is 2 inches. What is the radius of the circle?

224 inches

There ought to be an equation for this that would be far superior to trial and error, oui?


There is.

radius squared = (radius minus height) squared + (half the distance between endpoints)
squared

In this case:

r^2 = (r - 2)^2 + 30^2
r^2 = r^2 -4r +4 + 900
4r = 904
r = 226

I just drew that out. Clever. It's much more elegant solution than the
one I posted. Good work.