If the length of each edge of regular octahedron ABCDEF is 3, then find the area of triangle ACF.
+128475 Because of symmetry, the area of triangle ACF will be the same as the area of triangle EAC
EC is the base = the diagonal of a square with a side of 3 = 3sqrt 2
The height of this triangle = sqrt [3^2 - [(3/2)sqrt2]^2 ] = sqrt [ 9 - 9/2 ] = sqrt [ 9/2] = 3 /sqrt 2
So.....the area of triangle ACF = (1/2) [3sqrt 2] [3 /sqrt 2 ] = 9/2 = 4.5 units^2
