Board 1-- can't be completed
T2 triangle has lengths 1, 1 and Ö3

T1 triangle has sides of length 1.

Both triangles have areas of
Ö3
4

This means that the total area of the equilateral triangle must be a rational multiple of Ö3

Now, if both of these triangles are found at one of the vertices then one side of the triangle must contain a piece of length Ö3 and also a piece of length 1. Thus the length of the sides of the equilateral triangle must be A + BÖ3 where neither of A and B which can be zero. A and B
Board 2 -- can't be completed

No. If you could, its area would be a natural number because it is a sum of 1s and 2s. However, is would also be L*L*sqrt{3}/4 using the formula for the area of a triangle. You could only have one type of triangle on the edges for this to work. Imagine that the triangle was solely made up from one sort of triangle now. You'd have to remove a bit from the middle to get it to work. But you can't because youd need to replace one of the lengths with other lengths which wouldn't fit. Something like that.


Board 3 --Not sure....