It appears that this is always true, even if we have an obtuse triangle.....see the pic......

The reason for this is that ΔAEF will always have (1/2) the height of ΔABC, and it's base will always be (3/4) of ΔABC.
So Area of ΔABC = (1/2)bh = (1/2)(8)(16) = 64 cm^2
And Area of ΔAEF = (1/2)([3/4]*8)([1/2]*16) = (1/2)(6)(8) = 24 cm^2
