Find the partial derivative fxf_xfx of the function f(x,y)=arctan(y/x)f(x,y) = \arctan(y/x)f(x,y)=arctan(y/x).
−yx2+y2-\frac{y}{x^2 + y^2}−x2+y2y
xx2+y2\frac{x}{x^2 + y^2}x2+y2x
11+(y/x)2\frac{1}{1 + (y/x)^2}1+(y/x)21
−xy2-\frac{x}{y^2}−y2x