How many equilateral triangles in an octagon?

In an octagon, there are 20 equilateral triangles. Each side of the octagon can form two equilateral triangles with the adjacent sides, resulting in 8 equilateral triangles. Additionally, the diagonals of the octagon can form 12 more equilateral triangles. Therefore, the total number of equilateral triangles in an octagon is 8 + 12 = 20.