기록

7. Delta Notation $\frac{\partial J}{\partial \alpha }d\alpha =\int_{x_{1}}^{x_{2}}(\frac{\partial f}{\partial y}-\frac{\mathrm{d} }{\mathrm{d} x}\frac{\partial f}{\partial y'})\frac{\partial y}{\partial \alpha }d\alpha dx$ $\Rightarrow \delta J=\int_{x_{1}}^{x_{2}}(\frac{\partial f}{\partial y}-\frac{\mathrm{d} }{\mathrm{d} x}\frac{\partial f}{\partial y'})\delta y dx$ ($ \frac{\partial J}{..

6. with Auxiliary Conditions $g=\sum_{i}x_{i}^{2}-\rho ^{2}=0 \rightarrow r=\rho =constant$: Equations of Constraint (구면 위를 따라간다) $f=f(y_{i},y_{i}';x)=f(y,y',z,z';x)$ $g(y_{i};x)=g(y,z;x)=0$ $\Rightarrow \frac{\partial y}{\partial \alpha }, \frac{\partial z}{\partial \alpha }$ are not independent (하나의 variable이 바뀌면, 다른 variable도 바뀐다) $\therefore$ for $ \alpha =0, \frac{\partial y}{\par..