Hi at 1 Hour and 9 minutes this professor makes a derivation which i do not understand He is lecturing on newtonian mechanics and states that if dv/dt = a (acceleration) Then v*dv/dt = a*v And then he says that this is the same as d(v^2/2)/dt But I just can't undrestand how he did that last part? I know how to apply the chain rule to the derivative of a funnction of a function but i can't see how this applies in this example. The form he writes it on is f(x)*d(f(x)/dx (the same as v*dv/dt ) and the chain rule is on the form df(g(x))/dx = df(g)/dg * d(g(x))/dx? did he write it in a wrong mathematical form? What rule is he using?