(9) If a wire of length 1 is cut into three pieces, the probability that these three pieces can exactly form a triangle is . $\qquad$
(9) $\frac{1}{4}$ Hint: Let the lengths of the three segments be $x, y, 1-x-y$, then the total sample space is $x>0, y>0, x+y<1$. The area of the region where a triangle can be formed is $x+y>\frac{1}{2}$, area is $\frac{1}{8}$. Therefore, the required probability is $\frac{1}{4}$.