Determine the partial derivative fyf_yfy of the function f(x,y)=xtan(y)+ysec(x)f(x,y) = x \tan(y) + y \sec(x)f(x,y)=xtan(y)+ysec(x).
xsec2(y)+sec(x)x \sec^2(y) + \sec(x)xsec2(y)+sec(x)
tan(y)+ysec(x)tan(x)\tan(y) + y \sec(x)\tan(x)tan(y)+ysec(x)tan(x)
xsec2(y)x \sec^2(y)xsec2(y)
sec(x)\sec(x)sec(x)