I've been given this differential equation to solve:
Most of the steps are straight forward but I just can't get my head around the initial step that takes me from the equation above, to the one below.
I've heard chain rule mentioned but can't see how it is applied in this context. Any help would be appreciated.
Most of the steps are straight forward but I just can't get my head around the initial step that takes me from the equation above, to the one below.
I've heard chain rule mentioned but can't see how it is applied in this context. Any help would be appreciated.