what is the lengrth of an arc 16' wide and rises 12" in the center

Question

Need to make an arc that is 16' wide, and rises 12" in the centre. It'll be a perfectly curved arc. Need to know what the length of the beam for the arc should be. looked up formulas online but they all want the degree of the arc, but I won't have that until I build it. Would very much appreciate the help.

Answer 1

 

 Well then why not center the arc at the origin?

 The angle will be 180 degrees.

 

 One end of the arc is at x=-8 and the other at x=8.

 (0,1) is the max point of the arc as 1 foot = 12 inches

 

 The arc-length is then 1/2*pi*diameter = 1/2*pi*16 = 8*pi