(1) Two straight lines are cut by a third straight line and have the same angle. Conclusion: The isosceles angles are equal. This proposition is incorrect. Because only these two straight lines are parallel lines, the congruence angle will be equal. (2) An integer with a unit number of 4 must be divisible by 4: the unit number is an integer with 4; Conclusion: This number must be divisible by 4. This proposition is incorrect, for example:14,34, etc. Not divisible by 4.

(3) The vertex bisector is on the same straight line: the vertex bisector is on the same straight line. This proposition is correct.