Assume the base of the triangle is on the bottom four points because a congruent triangle can be made by reflecting the base on the top four points. For a triangle with a base of length 1, there are 3 triangles. For a triangle with a base of length 2, there are 3 triangles. For length 3, there are 2. In total, the number of non-congruent triangles is 3+3+2=8.
Isosceles triangles? I can find 12
but if you can rotate it of reflect it to be the same, it is counted twice.
Hmmmm.... ALL 12 of my triangles have the equal side lengths of 1.....and 4 have bases 0f 3 I guess there is only two that can be found?
The question says nothing about rotating/flipping being the same triangle..... I still think there is 16.....reflected / rotated / flipped makes it another triangle in the diagram ..... IMO