Answer:
√(21) / 2
Explanation:
The vertical line divides triangle ABC into two right angles which are congruent.
DB has length AB/2, which comes out to 3/2. Regard DB as the base of one of the two right triangles. If the height, CD, is √3, then by the Pythagorean Theorem |AC|² = (3/2)² + (√3)².
Thus, |AC| = √( (9/4) + 3 ), or √( (9 + 12)/4 ), or √(21) / 2