Question: basic input with x and xdot where (xdot is derivative of x wrt t)

How does one enter (and evaluate the following expression) in Maple

d/dt [ del(L)/del(xdot) ] = del(L) /del(x)

where "del" stands for the partial differential sign and "xdot" is the
simple derivative of x wrt t?

For example, I have L = 0.5*m*xdot^2 - mgx

 

Note that I understand f:=(x,xdot) -> 0.5.m.xdot^2 - m.g.x, but can't seem to make Maple realize that xdot = d/dt(x) within the partial derivative del(L)/del(xdot)

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