Why is D not efffective on (ln@cosh)

Question:Why is D not efffective on (ln@cosh)

Posted: C_R 3967 Product: Maple

1 hour ago

To D(ln@cosh) I have to add an argument to make it work:

D(ln@cosh)(x);
                            sinh(x)
                            -------
                            cosh(x)

According to ?D I expected output according to this

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