Define \(f:\mathbb {R}\to \mathbb {R}^2\) by \(f(x)=(x^2,x^3)\). Find \(f^*dx_1\).
Assume \(g:\mathbb {R}^2\to \mathbb {R}^2\) is a smooth map and for each \((x_1,x_2)\in \mathbb {R}^2\) the derivative is given by the
matrix \[ \begin {pmatrix} 2x_1+x_2 & x_1+3\\ \dfrac {x_1}{(x_1^2+x_2^2)^2} & \dfrac {x_2}{(x_1^2+x_2^2)^2} \end {pmatrix}. \] Find \(g^*dx_1\).