Answer
Isosceles triangle
Work Step by Step
We first assign letters for each midpoint:
$A: a,b \\ B: 3a, b \\ C: 2a,0$
We find the distances between each midpoint:
$d_1 = 2a \\ d_2 = \sqrt{b^2 +a^2 }\\ d_3 = \sqrt{b^2 + a^2}$
Since only two of the sides are congruent, we see that the triangle is isosceles.