Let us for a few seconds nevermind there's a circle at all, so we only really have a triangle by itself.
now, EF = 18, wait a second! EF is the base of the triangle, and h = 10.725, wait a minute!! "h" is the height of the triangle.
so, what's the area of a triangle whose base is 18 and has a height of 10.725? yeap, we knew you'd know that one.
what's the length of the arcEF? well, we know the central angle of ∡FOE is 80°, well, arc's get their angle measurement from the central angle they're in, so if ∡FOE is 80°, so is arcEF then.
