- The curve \(C\) has equation
$$x ^ { 2 } \tan y = 9 \quad 0 < y < \frac { \pi } { 2 }$$
- Show that
$$\frac { \mathrm { d } y } { \mathrm {~d} x } = \frac { - 18 x } { x ^ { 4 } + 81 }$$
- Prove that \(C\) has a point of inflection at \(x = \sqrt [ 4 ] { 27 }\)