area of octagon Watch
talk about dumb but i 4gotton how 2 work out area of a regular octagon can anyone show me how or give me a link to a website that tells me how. thanx
If r is the distance from the centre to a vertex of the octagon then the area of one of these triangles is
2 x 1/2 r cos (22.5) r sin (22.5) = 1/2 r^2 sin (45)
(by thinking of it as two right-angled triangles, say).
So the total area is
4 r^2 sin (45) = 2 rt(2) r^2