37. To two given straight lines, find a third proportional.

To two given straight lines, find a third proportional.
37. Let $A B$ and $A C$ be given lines, taken so that they form an arbitrary angle. Extend $A B$ so that $B D=A C$, and through point $D$ draw

$$
A B: B D=A C: C E
$$

$$
B D=A C
$$

$$
A B: A C=A C: C E
$$