(VAR x y )
(STRATEGY INNERMOST)
(RULES 
        D(t) -> 1
        D(constant) -> 0
        D(+(x,y)) -> +(D(x),D(y))
        D(*(x,y)) -> +(*(y,D(x)),*(x,D(y)))
        D(-(x,y)) -> -(D(x),D(y))
        D(minus(x)) -> minus(D(x))
        D(div(x,y)) -> -(div(D(x),y),div(*(x,D(y)),pow(y,2)))
        D(ln(x)) -> div(D(x),x)
        D(pow(x,y)) -> +(*(*(y,pow(x,-(y,1))),D(x)),*(*(pow(x,y),ln(x)),D(y)))
        
)