(유튜브 동영상인데 현재는 삭제되어서 내용만 남김)
개념
- $f, g$: 미분가능이면, $\Rightarrow f + g, \alpha \cdot f, f \cdot g$ 도 미분가능
- 연쇄법칙
- $f(x_{1}, x_{2}, ... , x_{n}), x_{i}$ 들이 $t_{1}, t_{2}, ... , t_{n}$ 에 대한 함수이면
- $\Delta f \approx {\partial f \over \partial x_{1}} \Delta x_{1} + {\partial f \over \partial x_{2}} \Delta x_{2} + {\partial f \over \partial x_{n}} \Delta x_{n}$
- ${\Delta f \over \Delta t_{k}} \approx {\partial f \over \partial x_{1}} {\Delta x_{1} \over \Delta t_{k}} + {\partial f \over \partial x_{2}} {\Delta x_{2} \over \Delta t_{k}} + {\partial f \over \partial x_{n}} {\Delta x_{n} \over \Delta t_{k}}$
- ${\partial f \over \partial t_{k}} = {\partial f \over \partial x_{1}} {\partial x_{1} \over \partial t_{k}} + {\partial f \over \partial x_{2}} {\partial x_{2} \over \partial t_{k}} + {\partial f \over \partial x_{n}} {\partial x_{n} \over \partial t_{k}}$