tan300°•cot287°+tan240°•tan193°-cot287°•tan193°
=tan120°cot107°+tan193°(tan240°-cot287°)
=-tan60°(-tan17°)+tan13°(tan60°-cot107°)
=
3tan17°+tan13°(
3+tan17°)
=
3(tan17°+tan13°)+tan13°tan17°
=
3tan(13°+17°)(1-tan13°tan17°)+tan13°tan17°
=1-tan13°tan17°+tan13°tan17°=1,
故答案为:1.