Question 18
In triangle $ABC$, $\angle B=90^\circ$ and $O$ lies on $AB$. A semicircle with centre $O$ and radius $OB$ meets $AB$ at $E$. The line $AC$ is tangent to it at $D$. Given $AD=2$ and $AE=1$, find the sum of the areas of triangles $AOD$ and $BCD$. Give your answer to one decimal place.
