The shape above is a cube and it has six faces. Each face is square in shape. Each square has diagonals.
Considering square BCGF, the square can be divided into two right angle triangle GBF and GFC using a diagonal line cutting across point GC.
According to triangle GBF formed, the diagonal BF serves as the hypotenuse of the triangle because hypotenuse is known to be the longest side of a triangle .
therefore the triangle that had hypotenuse as BF is triangle GBF and GFC
