I have a regular octagon with a radius of 9.

Question

I have split the 8 pie slices into right angles--leaving angles 90, 67.5, and 22.5. I looked for the sine of 22.5 opp/hyp and get .38. Then the oppositeside is 6.84. I can't get the right answer, what am I doing wrong?
Thanks

Answer 1

not sure what you're doing wrong, because you haven't said what you are trying to do. But if you want the side length, then if it is s, then you do have

(s/2)/9 = sin(22.5)
s = 18*.3826 = 6.888

Answer 2

I figured out my mistake. With thearea of the triangle, I forgot the .5
thanks steve, sometimes you need another perspective.