MathNet 2007-part-02 — 187 problems (EN–VI) Question 99

Two diagonals $AC$ and $BD$ of quadrilateral $ABCD$ intersect at a point $P$ in the quadrilateral. If we have $AC = 2$, $BD = 3$ and $\angle APB = 60^\circ$, what is the smallest possible value of $AB + BC + CD + DA$?