## Multivariable Calculus, 7th Edition

$\lt3sec^{2}(3x-4y),-4sec^{2}(3x-4y) \gt$
$f_x(x,y)=3sec^{2}(3x-4y)$ $f_y(x,y)=-4sec^{2}(3x-4y)$ Gradient vector field of $f$ is: $\lt3sec^{2}(3x-4y),-4sec^{2}(3x-4y) \gt$