Adjective should be in the same case as the noun with which he is bound. wysoki is nominative whereas policjanta is accusative.
And animate. For masculine singular Accusative, it also matters that "policeman" is definitely animate.
The rule is simple. If the noun is animate, its accusative takes the endings of the genitive. The same goes for all adjectives and pronouns that are modified by that noun.
Note that only the singular masculine gender has an animate subcategory and the change is only applied to the accusative.
I have no idea what a "tall book" is supposed to be, but that would be wysoką książkę. (feminine singular accusative)
Thanks, I missed my point.
I am trying to understand Jellei's comment about animate, presumably vs inanimate. So I would love to know how wysoki changes in the case of a masculine singular accusative inanimate object.
Clearly my level in Polish is not good enough to come up with an object that is masculine (I must not have paid attention enough).