Variation of Parameters: why do we assume the "constraint" $v'_1\left(t\right)y_1\left(t\right)+v_2'\left(t\right)y_2\left(t\right)=0$?
95888
Justifying an Assumption Made While Deriving the Method of Variation of Parameters
112179
Why don't the results of testing $H_0 : \beta = 0$ and $H_0 : {\rm cor}(X,Y)=0$ agree?
71092
What are the derivatives of position with respect to time
14656
The differential equation $xu_{x}+yu_{y}=2u$ satisfying the initial condition $y=xg(x),u=f(x)$
88491
Holonomic constraints and degrees of freedom
41489
Why $p(y_n|y_{0:n-1})$ is a constant in Kalman filter derivation?
85094
A problem from Evans' PDEs book: find a Lagrangian for a given Euler-Lagrange equation
157191
Conjugate Variables, Noether's Theorem and QM
88442
Prove that there's no ordered basis $E$ in which $T{x\choose y}={0\choose y}$ can be represented as $1\ 2\choose 2\ 4$
57630
Second order homogeneous differential equations: why do repeated roots modify the solution set?
61964
Is the principle of least action a boundary value or initial condition problem?
152293
Solution of $y''+xy=0$
109601
Does the equation $\displaystyle min_{x,y} f(x,y)=min_{y}min_{x}f(x,y)=min_{x}min_{y}f(x,y)$ always hold for a minimization problem?
75452
Initial value problem with $t$ and $x'$
26617
Minimum value of $ f(x,y,z)=\left(x+\frac{1}{y}\right)^2+\left(y+\frac{1}{z}\right)^2+\left(z+\frac{1}{x}\right)^2. $
122474
Inconsistency with partial derivatives as basis vectors?
126338
limits problem-ordinary sencond order equation