Editorial
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Editorial
Join $A,I$ for incenter $I$. $\angle IAD= \angle IAB = \angle AID$. Join $B,I$ and do the same thing.
In trapezoid $\square ABCD \text{, } AB||CD \text{ and } AD=5 \text{, } BC=3$. $BC \text{ and } AD $ intersect at $O$. If the incenter of $\triangle OCD$ lies on $AB$, determine the value of $AB$.
Join $A,I$ for incenter $I$. $\angle IAD= \angle IAB = \angle AID$. Join $B,I$ and do the same thing.