Answer
Both two vectors $\overrightarrow{CA}$ and $\overrightarrow{CB}$ are orthogonal.
Work Step by Step
Let $\overrightarrow{CA}$ and $\overrightarrow{CB}$ be the two vectors.
Now, $(-v+(-u)) \cdot (-v+u)=v \cdot v-v \cdot u+u \cdot v -u \cdot u$
and
$v \cdot v-v \cdot u+u \cdot v -u \cdot u=|v|^2-|u|^2$
when the both vectors posses same radius of circle then we have $|v|^2 =|u|^2$
This implies that $|v|^2-|u|^2=|v|^2-|v|^2=0$
Hence, we conclude that both two vectors $\overrightarrow{CA}$ and $\overrightarrow{CB}$ are orthogonal.
