21. Exemplar example problems I

1. If in the given figure, $O$ is the point of intersection of two chords $AB$ and $CD$ such that $OB = OD$, then triangles $OAC$ and $ODB$ are

 

 

2. $D$ and $E$ are respectively the points on the sides $AB$ and $AC$ of a triangle $ABC$ such that $AD = 2 \ cm$, $BD = 3 \ cm$, $BC = 7.5 \ cm$ and $DE||BC$. Then, length of $DE$ (in $cm$) is