1. The problem is to simplify or understand the expression involving $r/12$ instead of $\pi/12$. 2. We start by clarifying the difference: $r/12$ means the variable $r$ divided by 12, while $\pi/12$ means the constant $\pi$ divided by 12. 3. If you have an expression like $\sin\left(\frac{r}{12}\right)$, it means the sine of $r$ divided by 12. 4. Important rule: When dividing by 12, the entire numerator is divided, so $\frac{r}{12}$ is not the same as $\frac{\pi}{12}$ unless $r=\pi$. 5. If you want to simplify or evaluate, substitute the value of $r$ and then divide by 12. 6. For example, if $r=24$, then $\frac{r}{12} = \frac{24}{12} = 2$. 7. Always keep the variable and constants distinct and do not confuse $r$ with $\pi$. Final answer: The expression $\frac{r}{12}$ is simply the variable $r$ divided by 12, not $\pi$ divided by 12.