Figure 49 
The tangent plane \(\mathbf{r}( \theta ,y) =5\cos \theta\ \mathbf{i}+y\mathbf{j} +5\sin \theta\ \mathbf{k}\) at the point \(( -3,5,4)\).
The tangent plane \(\mathbf{r}( \theta ,y) =5\cos \theta\ \mathbf{i}+y\mathbf{j} +5\sin \theta\ \mathbf{k}\) at the point \(( -3,5,4)\).