Chapter 12.4, Problem 15ES

Use the formula $\text{B}\left(t\right)=\text{T}\left(t\right)\times \text{N}\left(t\right)$ to find $\text{B}\left(t\right),$ and then check your answer by using Formula (11) to find $\text{B}\left(t\right)$ directly from $\text{r}\left(t\right).$

$\text{r}\left(t\right)=3\sin t\text{i}+3\cos t\text{j}+4t\text{k}$