Question
For any vector $\vec{r}$, the expression $\left(\vec{r} \cdot \hat{i}\right)^2 + \left(\vec{r} \cdot \hat{j}\right)^2 + \left(\vec{r} \cdot \hat{k}\right)^2$ is equal to
For any vector $\vec{r}$, the expression $\left(\vec{r} \cdot \hat{i}\right)^2 + \left(\vec{r} \cdot \hat{j}\right)^2 + \left(\vec{r} \cdot \hat{k}\right)^2$ is equal to