Reasoning behind $\delta \dot q = \frac{d}{dt} \delta q$ in deriving E-L equations
101888
Least action principle : is $ \delta \frac{dx}{dt} = \frac{d \delta x}{dt} $ always true?
61073
Why is electric flux defined as $\Phi = E \cdot S$?
94230
I want to understand a trick in the derivation of the Schwinger-Dyson equations
100004
Differentiating $e^x$ from first principles using limits.
72604
The differential equation $y''-q(x)y=0.$
41407
How to derive or justify the expressions of momentum operator and energy operator?
20280
Proving that expression is equivalent to the definition of derivative
118072
Division of differential equations
105707
A proof of $\int_{0}^{1}\left( \frac{\ln t}{1-t}\right)^2\,\mathrm{d}t=\frac{\pi^2}{3}$
79024
the derivation of E(X|X)
54244
Understanding the Proof of L'Hopital's Rule
71885
Derivatives of $ \frac{1}{r} $ and Dirac delta function
8711
Problems in the relation $a=v\frac{\mathrm{d}v}{\mathrm{d}x}$
116513
Distributional Laplacian of logarithm and the Dirac delta distribution
67350
Analytic solution of: ${u}''+\frac{1}{x}{u}'=-\delta e^{u}$
65039
What is the reason of $dT/dh = 0$ in the gas column?
59518
MLE of $\delta$ for the distribution $f(x)=e^{\delta-x}$ for $x\geq\delta$.