Partial derivative of $xy\frac{x^2-y^2}{x^2+y^2}$
45363
Show that both mixed partial derivatives exist at the origin but are not equal
100007
Express partial derivatives of second order (and the Laplacian) in polar coordinates
139631
How to take this exterior derivative of the expression $du - \sum_i p_i dx_i$?
14548
Multivariable limit $\frac{(2x^2)y}{x^4+y^2}$
131357
Prove that $f(x,y)=xy$ is differentiable using the definition
17475
Find the derivative of $y= \frac{(4x^3 +8)^{\frac{1}{3}}}{(x+2)^5}$
91251
$n$th derivative of $e^{ax}\sin(bx+c)$
70438
Generalize Clairaut-Schwarz theorem to arbitrary order of mixed partial derivatives
95774
$\frac{\partial^2 u}{\partial t^2}-c^2\frac{\partial^2u}{\partial x^2}=0\text{ implies } \frac{\partial^2 u}{\partial z \partial y}=0$
109994
Show discontinuity of $\frac{xy}{x^2+y^2}$
52701
Manipulating Partial Derivatives of Inverse Function
94193
determine whether $f(x, y) = \frac{xy^3}{x^2 + y^4}$ is differentiable at $(0, 0)$.
66457
Series expansion of $xy'=y$
88137
$y''-2y'+y=te^t$ by method of undetermined coefficients
80471
Derivative of $(y-XB)' h(y-XB)$ with respect to $B$
84597
Derivative of $(1-x)^{-2}$
143375
Showing that $\lim_{(x,y) \to (0, 0)}\frac{xy^2}{x^2+y^2} = 0$