PLEASE HELP?

In a geometry class, the students were asked to write statements that are logically equivalent to the statement shown below.

If a line segment joins two points on the circle, then it is a chord.

Below are the responses of four students. Which student’s response is correct?

Student 2: If a line segment is not a chord, then it does not join two points on the circle.

Student 3: If a line segment does not join two points on the circle, then the line segment is a chord.

Student 1: If a line segment is not a chord, then it joins two points on the circle.

Question

PLEASE HELP?

In a geometry class, the students were asked to write statements that are logically equivalent to the statement shown below. 
  
If a line segment joins two points on the circle, then it is a chord. 
  
Below are the responses of four students.   Which student’s response is correct? 

 Student 2: If a line segment is not a chord, then it does not join two points on the circle. 

 Student 3: If a line segment does not join two points on the circle, then the line segment is a chord. 

 Student 1: If a line segment is not a chord, then it joins two points on the circle.

anonymous · Answer

Student 2 is correct, because he provided the contrapositive of the statement, which is logically equivalent.

anonymous · Answer

Thank youu @nbouscal