In triangle $ABC$, what is the value of $\vec{OA}\sin2A + \vec{OB}\sin2B + \vec{OC}\sin2C $?

In triangle $ABC$, what is the value of $\vec{OA}\sin2A + \vec{OB}\sin2B +
\vec{OC}\sin2C $?

Consider a triangle $ABC$ with it's orthocenter $ O$ being the origin.
Then what is the following equal to?
$$ \vec{OA}\sin2A + \vec{OB}\sin2B + \vec{OC}\sin2C $$
The answer given is $0$. Can someone explain how is this so?